Continuity mistake: While Donna and Bobby are in her bedroom at home, her toes are seen with no polish on. Donna goes to the bathroom to take some pills and returns. A closeup of her feet back in the bedroom shows her with red polish on her toes.
Plot hole: When the cop is in the room and he realises how the teacher escaped from the hotel, he pictures him walking out in the bellboy uniform while the cop is downstairs. However at this time he should be upstairs with the girl in her room, because he is still in the room when she runs out of the room into the cop. For this to work out, the teacher would have to have left the room before the girl even got there.
Deliberate mistake: It is shown throughout the film that card keys are to be used to open the hotel room doors; this is a security measure that is used for doors in elegant and expensive hotels (if not all). There are no hotels that use this measure without having break-safe metal material inside of these doors, yet the killer and cops are shown breaking down doors fairly easily. Add to this the fact that only thin slices of wood are shown breaking off of the doors, not metal nor even the card-keying device.
Continuity mistake: Despite being one of the few slasher films with a PG13 rating, whenever someone is stabbed, their bodies show no stab wounds when they appear again in the movie. The only character with blood stains where they had been stabbed has no holes in their clothing where the stab would have been, only blood stains.