When Little Miss visits Andrew to discuss her proposal from Frank, Andrew cuts off his right thumb. The stub left on his hand clearly shows a clean, straight cut. The severed tip of his thumb is not a clean cut.
When Andrew and Portia are playing chess in the park, the chess board is at first very unusually set up as most of Portia's pieces are on the board side closer to Andrew and vice versa. In the next moment, the board has changed completely.
'Sir' tells Andrew that he has stopped referring to himself as "One", however, during their first visit with Dennis Mansky at Northam Robotics, 'Sir' quotes Andrew as having said, "I enjoy doing this."
When Andrew goes to Lloyd to sue for information as to the whereabouts of his robot counterparts, Lloyd states "the Freedom of Information Act does not cover suits by robots.".
There is nothing in the act that states that it is exclusively for humans.
The final scene in which the nurse robot stops life support systems on request is invalid; the First Law of Robotics would have prevented it. No amount of begging would result in a positronic robot assisting in suicide or euthanasia. In fact, according to Asimov's stories, even witnessing a human being hurt might destroy a robot's positronic brain and the movie acknowledges the Three Laws of Robotics.
The delivery van that brings Andrew is supposed to be Electric, but it has a tailpipe which are not required for this type of vehicle. This is not a goof if the vehicle is a hydrogen or similarly powered vehicle which while running on electricity would have a water by-product which needs an exhaust pipe.
The goof item below may give away important plot points.
After Andrew obtains his fully human appearance, he correctly refers to himself as "a robot - well, now an android." The correct meaning of android is a robot who has a human, i.e. fleshy, appearance, as Andrew now does. However, earlier in the movie he and all other NDR robots are referred to as androids when they are conventional metallic robots. Andrew even derives his name from Little Miss's mispronunciation of the word "android".