Indiana Jones goes to Berlin in 1938, according to the movie. There he sees the infamous "burning of the books." In fact, the burning of the books in the Bebelplatz by the Nazis took place in May 1933. Certainly, all the Nazi-condemned books would have been long ago confiscated and destroyed by 1938.
When Marcus Brody is captured by the Nazis and put in a truck, the truck gate that is closed behind him has the insignia of the Afrika Korps (a palm tree over a swastika). The action takes place in 1938. The Afrika Korps wasn't formed until 1941.
Throughout the movie, many characters are seen utilizing firearms that were not in use at the time the film is set in. For instance, inside the castle, Indy and the guards make heavy use of MP-40 submachine guns, which were not introduced until 1940. The P-38 pistol is also used quite frequently, particularly by the Germans in the desert, and would have just been entering service in 1938. It is much more probable that the troops would have been using P.08 Luger pistols.
There are several different styles of uniforms worn by the German military and SS throughout this film. When Indian Jones is in Austria and Berlin, Germany the military uniforms are accurate for that period (mostly seen in the film is the M36 Field Blouse - with its characteristic bottle green color on a field gray uniform). However, while in the Middle East, the German soldiers are wearing the distinctive olive drab or khaki tropical uniform of the Afrika Korps (which was based off of the M40 Field Blouse design but with a lighter material). The Afrika Korps infamous insignia of the Palm Tree over the Swastika can be seen throughout the film on vehicles. Also while Indiana Jones is in the Third Reich (Austria and Berlin) while the M36 style uniform may be correct, many of the SS troops are seen wearing the visored M43 field cap; visored field caps of that style did not exist in 1938 (unless they were they heavy caps worn by ski troops -which are not present in this film). Elsa is seen wearing this style field cap during the latter part of the film. Lastly, throughout the film, many of the Nazis are wearing various types of World War II combat medals, even though this film takes place before the war and the creation of some of the medals / ribbons.
In the classroom where Indy shows the Coronado Cross to Marcus Brody, a few books are visible on the desk. One in particular "Living Egypt" was first published in 1969, 31 years after the movie supposedly takes place.
Kazim tells Indiana that his father is imprisoned in "the Castle of Brunwald on the Austrian-German border."
The movie is set in 1938, and from the scenes in Venice, it can be deduced that it's set at least in late spring, if not summer. Since Germany annexed Austria in March of the same year, there was no German-Austrian border when Kazim and Indiana conversed.
Shortly after escaping from the Venice catacombs, Indy and Marcus look at the rubbing that Indy scribbled off from the Knight's shield and it mentions the city of Alexandretta. Indy then later mentions that "the present-day  city of Iskenderun was built on its ruins", implying that Alexandretta was the past-name of the city and Iskenderun the present-name. In actuality, the city was still named "Alexandretta" in 1938, and didn't officially change its name to "Iskenderun" until the following year.
The Messerschmitt fighter planes that chase after Indy and Henry after they escape on the biplane from the Zeppelin are in fact Swiss-built Pilatus P-2 trainer planes, which were manufactured shortly after the end of World War II.
In the Berlin book burning scene, the uniform Indy changes into has the ribbon of the 1939 Iron Cross 2nd Class in the button loop. The movie takes place in 1938, prior to World War II and the institution of this award.
The beginning of the movie is set in 1912 Utah. The rank patch on Young Indy's Boy Scout shirt shows him being a Life Scout. Since the Boy Scouts weren't established in the US until 1910, while not totally impossible, there is little likelihood that Indy would have been a Life Scout by 1912.
When Henry and Indy were aboard the airship, the airships only departed from Frankfurt and Friedrichshafen, not Berlin, and were only making trips to the U.S. and South America, nowhere near Middle East, with exception of two trips on the Graf Zeppelin in 1929, long before the setting of the Last Crusade.
The initial scenes of the movie are shot in Arches National Park (which is, as is stated, in Utah), and the troop dismounts at Double Arch. Indy takes the Cross of Coronado from a cave near that arch. However, there was no train line for miles in any direction at the time of the story. The railroad line present in the area today was built during the 1950s to serve a uranium processing mill at Moab. The nearest railroad at the time of the story is 40 miles to the north.
The aircraft that Indiana and his father fly from the airship is a British Tiger Moth. This was an RAF Training aircraft and unlikely to be in the Luftwaffe in 1938 although there were trade agreements with the UK so it is possible to suggest that the Germans purchased a few. However by 1938 they had a fairly decent selection of their own aircraft to choose from.
The butler in the castle says "... and if you are a Scottish lord, then I am Mickey Mouse," but his mouth says "... then I am Jesse Owens". The line was altered in post-production because it was assumed that audiences wouldn't know who Jesse Owens was.
The last Luftwaffe fighter plane gets disabled by the seagulls flying up, and we see the propeller stop and hear the engine sputter out. Yet in the shot of the plane whizzing toward its fiery demise on the hillside, we hear its engine droning again.
In at least one scene, the SS officer Vogel is referred to as 'Herr Oberst' (Colonel), while his lapel insignia are those of a Standartenführer (SS equivalent to Colonel). An SS officer would have hated being called by an army rank.
When Indiana Jones first sees the tablet, he identifies it as an Early Latin text from the mid 12th Century. The text is not Early Latin, but rather Late Latin. Early Latin refers to Latin before the Golden Age of Cicero and Caesar. In the 12th Century, people used only Medieval Latin.
Elsa claims that she competed and won the silver medal in the 50 meter freestyle at the 1932 Summer Olympics for the Austrian swim team. In actuality, the event wasn't introduced in the real world Olympic Games until the 1988 Olympics in Seoul.
While Indy is in Germany, Colonel Vogel is seen wearing a black SS dress uniform. It is quite unlikely that he would be wearing a dress uniform in the field, and would more likely be wearing the gray field uniform seen later in the film.
The Rolls-Royce is in fact not a Phantom II but the smaller, cheaper 20/25; the engine displacement and power data is neither correct for the Phantom II nor the 20/25, and finally such a heavy car could never accelerate 0-100 km/h in only 12.5 sec if it only had the measly 30 bhp the character talks about. As a reference the real Phantom II could only do 0-100 in 14.5s despite having a peak power of 122 bhp.
When Colonel Vogel is in the desert with the party heading towards the site of the Grail (at 1h24m), he says "It must be within three or four miles, otherwise we'll be off the map". He's supposed to be a German, and in Germany, the metric system was the official system of weights and measures since the formation of the German Empire in 1872, and metrication efforts had begun in the German states,kingdoms, and principalities since after the Napoleonic Era in the early 1800s. He would have said "It must be within five to seven kilometres..." instead.
The crucifix shown on the old knight's tunic is not a type
associated with Western Christianity in its Catholic form. It is, however, used commonly by the Greek Orthodox church. The Crucifix used by the soldiers of the First Crusade was an even-legged variety and nowhere near as complex as the one shown in the movie. Perhaps he obtained this item from someone else.
Indiana Jones in "Raiders of the Lost Ark" ultimately encounters all of the powers of the Ark of the Covenant. Yet when he becomes involved in the search for the Holy Grail he is dismissive of it as legend. Surely his experience with the Ark would have given him some sort of belief in the existence in a higher power and the stories associated with it.
The large X at the library is shown dark with a white background and a red frame when Indy is looking at it from the top of the staircase, but it has no white background when he starts breaking the tiles a few seconds later.
During the tank scene Indy is caught on the gun barrel by a strap, a situation from which he can't extricate himself. At the end of the fight however he is shown jumping back up onto the tank without untangling himself.
In the library scene Indy discovers the "X" high up on the balcony. The X is green with a grey background. But when he breaks the tile to find the tomb the X has disappeared and the ground is a solid green.
Indy and Elsa's boat is hit by submachine gun fire and sputters out, dark smoke billowing behind them. Elsa maneuvers the boat away whilst Indy duels on the other boat. When Indy is done fighting and his boat is being chopped to bits, Elsa maneuvers the boat back and ably picks up Indy and Kazim. That same boat (same bullet holes in the windscreen) is speeding down the Grand Canal a few moments later.
When Indy and his father are in the airplane while escaping the zeppelin, Henry shoots the plane's tail, ripping the top off. In subsequent shots of the plane, the tail can be seen with holes in it, but the top intact.
When the Joneses are watching the oncoming German vehicles from a hilltop, the sun is behind them (Henry's shadow moves) - but the sun is also behind the Germans (they see its reflection in Indy's binoculars).
Indiana completes his fathers shield pressing by rubbing it with a crayon or something similar to it. However, moments after he is forced into the petroleum with the rubbing in his pocket. Even if the wax somehow stayed in-tact, surely the tracing paper it was on would have destroyed, in part, some of the shield text. Yet we see it later looking just fine.
When Indy first arrives at the castle, it is nighttime and pouring rain. In the next scene when Donavon leaves, he is shown getting into a car at night. A few minutes later, when Indy and Henry escape, it is the middle of the day and there are no puddles or anything to suggest it had been raining recently.
When Indy is hanging from the gun barrel on the side of the tank as it is grinding into the side of the cliff, the strap of his bag is looped around the barrel, which was too long for the bag strap to have gotten looped around it.
When talking about the map and that Jones' father knew everything except the name of the city, Brody closes the diary and starts the rubber band on. In the next shot he is holding the opened diary again.
When Henry Jones enters the tank to rescue Marcus, the tank's crew and/or additional soldiers are not inside. Colonel Vogel then enters the tank with two aides. When Donovan from the outside informs Vogel that Indy is getting away, Vogel closes the tank's hatch and the tank's engine appears to start, signifying it is on the move. However, at no point did we see the tank's driver or additional crew enter the tank, whom we see in later inside shots of the tank. This suggests a lapse in continuity. If the tank's crew entered after this scene, Vogel's closing of the hatch appears to be entirely redundant.
When Indy is standing in his father's ransacked house, he pulls the still-wrapped diary out of his pocket along with a couple of white envelopes. In one shot he throws the white envelopes on the floor just before ripping open the diary, but in the next shot he's still holding the envelopes.
In the library scene in Venice, the librarian stamps a book twice and places it on a stack immediately above two books with blue pages. In the next shot of the librarian, there are two books between the one with two stamps and the 'blue books'.
When Indy finds the "X" on the wall inside the catacomb, the wall is intact. When the shot goes back to Indy from Elsa, the wall is partially crumbled, but there is no noise or anything to suggest it was knocked over by force.
While the small boat is being destroyed by the propeller, Indy and Kazim leap from it onto the second boat being driven by Elsa. In the shot just before the jump, the boat is whole again. Then, its back to the destroyed one.
When the plane used by Indy and Henry hits the ground, there is a close-up of the undercarriage collapsing under the force of the impact. However, it is clearly intact in the next shot, when the plane taxis towards the wall.
Indy's face is almost black from dirt and grime when the tank's gun is grinding dirt onto him from the wall, yet after he climbs up from the side of the cliff to join the others his face is hardly dirty at all.
In the boat chase sequence, the film is flipped horizontally to preserve the continuity of the boat's motion. This causes a reversed image of the boat and its interior (Indy, Elsa and the steering wheel swap sides).
When Indiana is fighting on top of the tank just before he drops the gun to his father, you can see he is losing his hat. However when the film cuts back to him moments later it is secured on his head once more.
During the fight between Indy and Kazim, an end section of the boat's windscreen can be seen sliding off the bow and tipping towards the water just as the camera cuts to a view from behind the boat. From this angle, the piece of windscreen can be seen lying flat on the boat's bow and not moving. When the camera switches back to the original angle, the piece of windscreen is gone.
When Indiana & Dr. Schneider arrive at the castle in Salzburg, Dr. Schneider is wearing a plain style beret. However, when the door is opened & Indiana is wearing the beret, it changes to a french style beret with band & tab on top.
When Indy and gang are racing the Nazis to the canyon of the Crescent Moon, Indy looks at the Nazi convoy with binoculars. Close-ups of Indy show the sun is clearly behind him, and the binoculars are in his shadow. But then a glare from the lens alerts the Nazis to their presence.
In the temple in the Canyon of the Crescent Moon, Indiana Jones rushes to his father's aid with the Holy Grail filled with water. He is shown pouring every last drop onto his father's wound by turning the Grail upside down, yet another camera angle shows his father clutching the grail to his chest, and there's still a bit of water in it.
After Elsa and the German colonel leave the room after saying goodbye when Indy and his dad are tied up, it shows Elsa and Donovan leaving in cars when it it dark outside. During the next few scenes when Indy and his dad escape they come outside by some motor boats and it is daytime.
When Elsa drops the grail during the earthquake, the earth splits directly below where the grail landed, but in the next shot, it's a few inches away and Elsa accidentally kicks the grail into the crevice.
Jones Sr., inside the tank, shoots a cannon at a truck next to the tank. The truck explodes, and a (dummy) body flies up and toward the tank. But in the next shot, the body falls on the other side of the smoke cloud, far from the tank.
During the library scene when the librarian is stamping books, you see him holding the stamp one way when Indi is banging on the floor. When they cut the angle from the front of the librarian to the side, he is holding the stamp a different way. When the camera angle returns to the front, he's back to holding it the other way.
During the escape from the Nazis the Jones boys pass through a boathouse and Indy sets a small boat loose with the engine running to distract them. When he releases the boat the motor (and boat) is turning to the starboard side (which would turn the boat straight back into the bank), but when the Nazis arrive, the boat is running perfectly straight down the river.
While Indy and Marcus are in the apartment in Venice, after Marcus says, "He knew everything, except the name of the city", he slams the diary shut. Then it's shown open, and he closes it a second time. When Indy takes it, it's once again open.
At one point Indiana's father blows the tail of the plane in which they were flying to pieces in an attempt to shoot at the Germans. This is obviously in a close-up studio shot. The next moment the plane is shown flying in the distance with its tail still intact.
When Indy is first knocked over the side of the tank and stuck hanging on the gun looking up at Colonel Vogel, you will notice Vogel's right shoulder strap is unbuttoned. Later as he battles Indy on the tank, the shoulder strap is buttoned back up.
When Indiana and Dr. Schneider arrive at the castle in Salzburg, Dr. Schneider is wearing a plain beret. However, when the door is opened and Indiana is wearing the beret, it changes to a French-style beret with band and tab on top.
When Donovan, Brody and Elsa are riding in the convoy in the desert, Colonel Vogel walks alongside the car and talks to Donovan. After having a drink, he steps back from the car and walks backwards down the convoy and we see that the Colonel has clearly passed the first car. In the next shot where Marcus says, "You are meddling with powers you cannot possibly comprehend," the Colonel is not in the shot, stepping into it later as if he had still been alongside the first car.
At various points during the tank chase, we see Henry Jones from the inside looking out of the small port on the side of the tank. This port, however, does not seem to match the exterior shots of the tank. From the outside, the port is located on the sponson directly beside the side gun. On the inside, however, it is located behind the sponson, further down the wall and therefore closer to Henry Jones to look out of.
After Henry subdues the Nazi soldier inside the tank with his fountain pen, we see the tank's right turret pointed straight at the driver's side window of an army truck driving alongside the tank, but when Henry runs over and fires the turret, the shot hits the truck on the rear compartment, behind the driver's side.
When Indy first starts wrestling with the thug on the roof of the box car with the rhino inside, he falls on his back and the camera shows it from a distance. Clearly, the roof has already been partially destroyed. The tar paper is broken and wood is showing even though the rhino still hasn't started pounding the ceiling.
When Indy steps on the wrong letter with his right foot, we see it collapse under him and we see clearly that only his right leg falls through - his left leg stays on the solid ground behind him, yet in the next shot, from underneath, we see both his legs fall through at the same time.
When Indy and his father are escaping from the castle, right before the motorcycle chase, they set off an empty boat to distract the Nazis. Inside the boat there is a blanket and if you look closely you can see an arm that comes out from under the blanket and grabs the boat's rudder.
As Fedora runs after Young Indy after discovering the magic box is empty, he opens the back door. A crew member in a white shirt can be seen sitting on a railing in the glass reflection of the caboose door on the right side of the frame (may be visible in widescreen version only).
When Indiana finishes crossing the invisible path and enters the room with the grail and the knight you can just see the shadow of someone moving (its definitely not the knight's shadow and there wasn't a hat on the shadow either so it's not Indiana, either).
When Indiana Jones and the rest of the gang are escaping the crumbling tombs where the Grail was housed, you can see a man in a white tee shirt and jeans off to the right side just before Henry Jones looks back at the Knight.
Unlike Rome, Italy, there are no catacombs beneath the city of Venice. If there were, they would certainly be below the water table and very likely flooded. Furthermore, there is no rock beneath Venice in which catacombs could exist. Venice is built on mud flats with hundreds of meters of poorly consolidated sands, silts, and clays below that. The foundations of the buildings are wooden pilings driven into the mud.
Though it is not stated in which months of 1938 the movie takes place, from the weather someone can guess it's late-spring between early fall. State Of Hatay is formally established in September 1938 and joined Republic Of Turkey in 1939. Moreover, during its short existence, it had never any royalty, it was established as a republic.
The beginning part of the movie is set and filmed in Moab, Utah. But when the Young Indy is being chased by men onto the train, they quickly go through some forested land for a long time, with a green meadow. The nearest landscape like that would be in Southwestern Colorado, or Central Utah, not Eastern Utah as depicted.
Blasting holes through the rudder of a small plane will not disable it, especially when Jones Sr.'s body was enough to cause wind drag. Although level turning would be impossible, the plane could still maneuver with the wing ailerons, which are more critical to level flight if ever damaged.
The entire sequence with Indy hanging from the splayed barrel of the tank is wrong. First, there is no way the strap on his satchel gets out and around the splaying for him to get caught. Second, when he realizes the strap is caught he acts like there's no way to get out. The strap is under his arm pit. It'd be easy enough to raise his arm and drop off. Third, after the tank abruptly swerves away saving Indy, in the next shot he's just jumping back up on the tank - satchel in place. How did he do that? He'd have to get the strap back out around the splayed barrel.
In the famous motorcycle chase scene, Indiana thrusts a flagpole into the spokes of a pursuing Nazi's motorcycle, and both Nazi and bike go flying almost straight up. In MythBusters: Motorcycle Flip, it was proven that while a flagpole theoretically could stop a speeding motorcycle, under no circumstances could it possibly leave the ground - much less go flying upwards.
There are a number of factual errors involving the Zeppelin seen in the film. The registration is given as "D-138." All actual Zeppelins used for passenger travel had a registration number in a "D-LZ (number)" format. Even if this number was meant to be consistent with actual Zeppelins, no real life Zeppelin was built after the D-LZ130 Graf Zeppelin II, which was manufactured alongside the Hindenburg but was never used for commercial travel. Finally, the film is set in 1938, and no commercial Zeppelin travel continued following the Hindenburg disaster in May of 1937.
After the caption establishes the setting as REPUBLIC OF HATAY, Donovan addresses the Sultan as "Your Royal Highness." Although there have been exceptions, the usual distinction of a republic is that it has no royal family. This particular short-lived, unrecognized republic was governed by President Tayfur Sökmen and Prime Minister Abdurrahman Melek throughout its brief existence.
When Father and Son have to escape the Blimp on an open air Biplane you'll notice during the close-ups of the dogfight between the planes both Jones not only have no problem keeping their hats on there's virtually no wind blowing their hair or anything else. This is clearly shot in a studio with a green screen, but it's glaringly obvious someone forgot to at the very least bring the fan to the shoot.
In the word of god challenge, Indy presses on J and the stone collapses. The J stone is in the first raw of stones. When Indy slips through that space, from an under shot we can see the area. There are some support columns, apparently for correct letters, and the rest of the stones have no support indicating they are all trap stones. Yet, Indy's position is a few feet into the support-less stones where he should be at the beginning.
When Indy goes to Venice he is flying on a Douglas DC-3, which has a maximum range of 1,491 miles. The background flight path shows the plane flying from Newfoundland to the Azores, a distance of 3.198 miles, all over water. The airplane would have run out of fuel less than half way across the ocean.
On the second task, when Indy is about to step on the "J" we can see the next tile is labeled with a "Y". When stepping on the "J" it crumbles and Indy holds to the tile right in front of him to avoid falling. As he hangs himself from the "Y" tile, and this isn't part of "Iehovah" either, the "Y" tile should have crumbled and Indy should have fallen.
After Donovan drinks from the false grail, he ages rapidly, shown by, among other things, the hair on his head growing to a great length. Since facial hair grows more rapidly then the hair on our head, he should have had a very long beard as well.
When Indy has fallen into the fissure and is reaching for the Grail, Henry is holding him by the wrist and he is dangling. However, when the camera angle shifts to over Indy's shoulder, you can clearly see his left hand holding on to an outcropping.
The Boy Scouts of America originated in 1910,. Young Indy is wearing a life scout patch while his friend is wearing either a scout or tenderfoot pin. Life scout is the sixth rank, just before Eagle which takes an average of four years to achieve, however, even if Indy had achieved Life in two years he would not have been wearing a patch as the patches were not introduced until 1913, like his friend Indy would have been wearing a life pin.
It has been suggested by many viewers that the X on the library floor is missing when Indy attempts to break through. In fact it is still there and is visible. It isn't nearly so obvious as when viewed from above, but that's rather the point they're making.
Although the German Zeppelins could carry cargo (the Graf Zeppelin carried a car to South America), they were not equipped to carry and launch airplanes. Only the rigid dirigibles used by the US Navy could launch, retrieve, and house airplanes. However, the Indiana Jones films are largely intended as an homage to the movie serial segments of the 1930s-1940s, and some artistic license was clearly taken throughout the series for the sake of exciting action/adventure visuals and scenes. Additionally, some actual trapeze connection attempts on the Hindenburg were made in real life by World War I flying ace Ernst Udet, so this is not outside the realm of possibility.
The tank used in the Nazis' expedition to the Holy Grail is a version of a World War I British Mark IV model, not a 1930s Panzer unit that would have been commonplace in the German army by then. That's because the tank was provided by the King of Hatay (who would be much more likely to have vintage British Tanks than Brand new German Panzers) rather than the Nazis.
When Vogel finds Indiana and Henry Sr. on the zeppelin, the newspaper Henry Sr. has is seen upside-down. This is obviously the incorrect way to read anything, but Henry Sr. was most likely simply trying to hide from Vogel and used the newspaper to block his face. Furthermore, he is seen without his glasses, which he uses all the time. He wouldn't be able to see anything clearly without them, much less read the newspaper.
In the beginning, young Indy removes a snake from his friend saying "It's only a snake", but in the earlier movies older Indy was afraid of snakes. This is, however, clearly intentional: Indy does not gain his fear of snakes until he falls into a full crate of them a little later in the film.
When Marcus shows Indy the diary's map in Venice, the map is shown depicting a river running from an oasis and snaking across the desert into the mountains and leaving straight into the Canyon of the Crescent Moon. Later in the movie however, once everyone follows the map's trail to the Canyon, we see no river nor any other body of water whatsoever. However, the map in the diary is based on much older information. The river dried up over the centuries.
While talking to Indiana in the boat, Kazim's shirt is open, then closed again so he can re-open it to show his tattoo. This is because the scene was originally longer. Indiana accidentally ripped open Kazim's shirt, revealing the tattoo while questioning him. The complete scene still appears in the Marvel comic adaptation.
When Indy and Marcus are looking at the rubbing made of the Grail tablet in the catacombs in Venice, it is completely dry and the paper is undamaged. This is not possible if after Indy had made the rubbing he then swam underwater through petroleum. The paper would have become soaked and then disintegrated.
While in the catacombs below the Venice library, Indy makes a torch from a bone and cloth of one of the corpses. He then dips the cloth in the petroleum for fuel, and is able to keep it lit. Later, Kazim drops a match into the petroleum, igniting it up to where Indy and Elsa are. Despite the fact that Kazim himself isn't killed doing this, for some reason, Indy's torch never ignites the petroleum as lighted pieces fall off into it.
When Henry Sr and Jr (Indiana) escape in the Zeppelin Plane, during the WHOLE flight (in close-up shots) there is no sign that they are flying, or even that high in the air. Nothing flaps, moves, flutters... notice that their hats are perfectly still. At that altitude, let alone flying an open cockpit plane at high speeds, there would have been a lot of wind. The shots were obviously done on a stage where someone forgot to turn on the wind fan.
When the tank's gunner fires the plugged cannon, the cannon's firing-trigger is already positioned all the way back in the trigger-guard, so the gunner could not have pulled it back further to shoot the cannon.
During the library scene where the large X is on the floor, Indy climbs a spiral stair case to get a better look at the floor. When he's at the top, the book case behind him is clearly made up of book spines glued to a black background.
As young Indy, played by the late River Phoenix, is trying to evade Fedora and his men, he is not wearing any gloves during the chase. Fedora then calls down to Indy in the lions den boxcar to toss the whip up so he can pull him out and retrieve the cross. As he's pulling him up, Indy is now seen wearing a glove on his right hand and holding some sort of contraption that wasn't there before. The scene then cuts immediately to Indy popping out the top with his hands both bare and no sign of the glove. The glove was probably used in making the film for protection of River's and/or the stuntman's hand, while the contraption he's holding maybe some form of bait to attract the lion. The scene cuts very fast and I'm sure back in 1988, the filmmakers weren't thinking about DVD's and the pause-step feature for movie buffs to capture all the mistakes and goofs that were made.
When Indiana steals the German Officers uniform to disguise himself at the book burning rally, he doesn't take the uniform pants. When he first emerges from behind the car you can see he's still wearing his khaki pants, which would have been easily spotted by anyone there, especially Hitler.
When the tank falls off the cliff and hits the ground below, the turret falls off, revealing a flat surface underneath on the chassis model - there's no way for the occupants to climb out from the body of the tank through the turret, as we see them do several times previously.
In the library, when Indiana opens the grail diary to look at the roman numerals, there is a scrap of paper under Indy's right thumb. The article on the scrap of paper mentions the years 1939, 1941, 1942, and 1943 in the past tense, where the movie is set in 1938.
After Donovan drinks from the false grail, he begins to age rapidly in a matter of seconds. For reasons not explained, his clothes also age with him, although he never seemed to get any of the holy water on them.
When Indy jumps on to the tank, Colonel Vogel sticks his head up. In the shot from behind his head, the flag on the back of the tank is fluttering in the wrong direction, towards the front of the moving tank.
When Indy & Co. are discovered by German guards in the temple, the last guard shouts "Achtung, Überfall" which translates to "Look out, robbery". It makes no sense at all for a German guard to shout that at this point and location.
The goof items below may give away important plot points.
In the Word of God challenge, "Jehovah" is used as God's name, but the name "Jehovah" was created for the King James Bible in the early Sixteen Hundreds and was a linguistic corruption of the Hebrew "Yhwh." or "Yahweh." It would not have been used by an Eleventh Century knight.
When Donovan drinks from the false grail (at least 800 years old if it was brought by the knight, supposedly older), a steel hexagonal nut holding the base to the stem is clearly visible as Donovan tips the goblet.
Indy makes a mistake during the Word of God challenge and steps on a J as the first letter in Jehovah. During the time period that the cave structure was excavated and the "tests" first constructed, there was no letter "J" in the Latin alphabet. It didn't appear until the 14th century, and was not in common use until the 17th century.
When Indy is fighting on the tank, his father falls onto the tracks and Indy uses his whip to stop him from going over. Then when Sallah rides up on the horse to rescue Indy's father, Indy is seen throwing the whip to Sallah on the horse. After the tank falls off the cliff Indy is seen with the whip attached to his belt before any one even notices he is alive.
After the tank driver is hit by the ricocheting bullet, he falls dead on the tank's directional lever, causing the tank to make a hard turn to the right (thus saving Indy from colliding into the rocks while hanging on to the side turret). With the tank driver's dead body leaning on the lever, the tank should therefore keep turning to the right and going in circles, but for the next several shots, the tank instead continues to go in a straight line before going over the cliff's edge.
When Indiana returns to his dying father with the Grail full of water, he empties the Grail completely on Henry's bullet wound to heal him. But a few moments later, when Henry takes the Grail from Indiana's hand, it still has water in it.
When Indy is hanging from his father's hand trying to get the fallen grail, his hand is shown to be slipping in close shots, yet wider angle shots show that Henry is holding him by the wrist and not the hand.
When Elsa is reaching for the grail while holding onto Indy, the glove on her right hand starts slipping off. At first, it is seen slipping up to her fingers, but then it is seen again, this time still mostly on her hand and only slipping to the palm. The glove then slips off completely.
After Henry has drunk the water from the grail, he is looking at it while holding it in his hands and you can see the small light in the bottom of the cup that is making it "Glow". The Glow comes and goes from time to time.
Disguised as a steward on board the Hindenburg, Indy repeatedly asks for a 'fahrschein', which would be a ticket for land based vehicles, yet none of the German passengers even flinch. The later released German dubbed version fixes this by using 'flugschein' instead.
The one surviving knight is at least 800 years old. As he has had no contact with anybody since then, he shouldn't be able to speak modern English. But in the classic B-movie genre which Indiana Jones imitates, English is the lingua franca of the universe, as the audiences are expected to have little patience for subtitles. Space-aliens and Ancient Egyptians speak English in those types of movies, a tradition continued here.
For the Word of God challenge, stepping onto the wrong letter tiles will cause the tile to crumble and send the person falling into the chasm below. When Indy steps onto the J tile by mistake, he falls through, but grabs onto several of the other floor tiles to hoist himself back up. The I tile (the first correct tile) is nowhere near the J, which Indy fell through, so by grabbing onto the other nearby tiles to hoist himself up would be putting weight on them, much like stepping on them would, therefore those other tiles should have also crumbled. This is further backed up when Indy steps on the O tile and accidentally touches his heel to the P tile behind it, and just that slight touch causes the P tile to crumble.
At the bridge at the end, the invisible bridge is shown to be an optical illusion caused by the bridge being carefully painted to blend in with the cliff behind it. When the illusion is exposed the camera moves just a few meters to Indy's right to reveal where the bridge is. However, during the sequence we several times see Indy in reverse angle, i.e the viewer is on the far side of the bridge looking back at him. From this angle the painted bridge should be obvious to the audience, as it can't possibly be painted to blend in with both cliff sides at the same time.
In the scene at the temple when Indy is "walking the name of God" and falls through the floor after stepping on the wrong letter, the debris falls with him on the cutaway shot, but then strangely disappears as it passes behind an outcrop of stone instead of continuing down.