Continuity mistake: When Evan comes into the flat and walks towards the window, pay attention to the sink, there is a red cup or something in it. However when his arm gets stuck in it, there is nothing red in the sink, and there was no time for him to take anything out of the sink.
Add timeRonnie Bischof
Revealing mistake: When Nora's son gets killed, we can see the boy under the falling piece of glass. But in the shot where this piece is just about to smash him, you can see on the DVD edition that there is a dummy instead of him because his arms are too long relatively to the whole body and also the hands are obviously not human.