Susan is laying on the bed with one leg dangling over the edge, waiting for David to return from checking downstairs. You see her leg in the mirror, dangling, foot not touching the floor. The camera then goes to a close up, floor level, of a hand reaching for Susan's foot, which is now touching the floor. Right before the hand grabs her ankle the camera goes back out to show Susan and the mirror. The mirror clearly shows Susan's foot off the floor again with the hand around it.
When Susan and David are having coffee with Reverend Swan, her ponytail is draped on her shoulder. It jumps behind her and back several times without her touching her hair.
When the killer attacks the rock star (in the final massacre-scene), he has a knife in his right hand when they fall to the ground. The knife is no longer there when the killer lifts the rock star by pulling his arms. In the next shot the knife is back in the killer's hand, while he is holding the knife and the rockstar's arm with the same hand.