Other mistake: Maureen cuts her wrists with a razor blade. Days later, no bandages or scars.
Audio problem: In the scene after Norman goes for a late-night swim, when he's telling Maureen that he slipped in the mud, you can see that his mouth never moves, yet he speaks the words "I slipped in the mud."
Revealing mistake: When Norman drives Dukes car into the pond, it's obvious no one is in it.
