Deliberate mistake: When Humbert is walking through Quilty's mansion at the start of the movie, a bottle is placed near the top of a chair covered in a sheet, which is later revealed to be covering Quilty; the bottle is also shown to be placed on top of Quilty's head. This same scene is shown a second time at the end of the movie, but the bottle near the top of the chair cannot be seen. There is a second bottle on Quilty's lap that can be seen in both the two scenes, but the bottle on Quilty's head cannot be seen the second time around. The two scenes were likely filmed two seperate times. (00:02:50 - 02:32:18)
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)