Deliberate mistake: In Raymond's flashback to "when he was once loved" there is a scene where he is having dinner with the Senator and his daughter. Evidently someone didn't feel that this scene was quite long enough as shot. Raymond picks up a piece of meat on his fork, puts it in his mouth and then begins to laugh. Then he puts the empty fork back into his mouth, removes the piece of meat and replaces it onto his plate. Obviously, the film was reversed briefly to give the illusion of a longer scene.
Deliberate mistake: When Humbert shouts Quilty's name when he is in his mansion, a bottle can be seen rolling off a chair covered in a sheet in the background. It is then revealed that Quilty was sitting on the chair, with the sheet covered over him, and the bottle was placed on top of his head, over the sheet. It is also shown that him waking up was what caused the bottle to roll off the chair. The bottle's position on the chair before Quilty awoke could not have been possible. Even if Quilty was able to place the sheet over him before passing out, he could not have been able to place the bottle over his head and he could not have been able to balance the bottle over his head whilst he was asleep unless he remained completely still all throughout his sleep. This was likely done deliberately as a way of letting Humbert and the audience know where Quilty was, but still make little sense in the context of the movie. (00:03:25)