In the scene where Arnie's daughter tries to break out of the room with the boarded up windows, she removes the doorknob by unscrewing the grub screw and pulling on the handle. This would result in the handle on her side of the door coming off without the shaft attached! In the film, both the handle, and the shaft come off together, which is impossible. Even if we are to believe things the way they have been presented, the handle on the outside should have fallen, with no shaft to support it.