Crew or equipment visible
Errors in geography
In fact, it is the corridor of those type of train coaches that is platform-side.
Incorrectly regarded as goofs
In a deleted scene it was confirmed. And despite so, the taboo was put in place to find Harry and a handful of others who were brave enough to say his name. By this point Voldemort is going to attack Hogwarts and his followers are already there/going there. No point in having the taboo if you are already going.
He probably used a defensive charm of some sort. Not to mention at this point Voldemort was slowly losing his power and his spells/jinxes/charms weren't as strong.
Right before James goes through the barrier, Lilly gets off to walk through with Ginny.
She had her hair in a bun/ponytail. It might have fallen out of the bun in the chaos going on.