Revealing mistake: When Rik jumps in his bed with the magazine and the circular saw comes out, watch closely and you can see the bed and sheets are already in two halves.
Revealing mistake: When the vampire is shaving himself in the toilet, the reflection in the mirror of his shaving cream, clothes and gloves is almost, but not quite, identical to his movements. The empty suit in the mirror and the visible part in front of it were shot separately by copying the other part's movements as closely as possible, as the surviving raw footage can prove. It's hard to see, but there is a small difference between the motion of the hands.
Answer: Madness.
jle