When one of the girls trips over a dead body, between three shots, John's dead body on the floor changes the way is it lying.
While looking for Malissa (Ria Pavia), who has already been killed, Shawn (Scott Fults) is grabbed by the killer and dropped downward on to a three-spiked sculpture that impales him, from back to front. He's shirtless and wearing jeans during this scene. When the pair are later uncovered in the closet and fall out, Shawn has one nearly bloodless exit wound on his chest, no entry wounds on his back, and is in his underwear.
When the dead pair falls out of the closet, you can see the guy breathing clearly. Position of the girl remains the same in other shots, even when the other girl moves her head in one shot.
When the killer is slapping the nude girl's face, on top of the elevator, it is clear than most of them miss contact with her, and also the sound effects that go with the slaps are awfully out of sync.
Obvious fake head when girl is beheaded.