When the evil forces caused the elevator to malfunction, the man inside is shown pressed against the ceiling as the elevator is rapidly descending. The only way this could happen is if the elevator was accelerating downward faster than the force of gravity could pull it. That he should stick to the ceiling is against the laws of physics.
After the opening credits as Mr. Caswell escorts Melanie and John into the front door, you discover that the perspective view of the foyer in the background of the doorway is fake. There is a gap between the prop background and the top of the door frame where the side of a staircase can be seen ascending in a different direction than the one seen later in the film.
A character's right arm catches fire as they sit in the driver's seat of their car. In angles from the side showing the burning arm, it's either a stuntperson's or a prop stuck between the two front seats: its movements don't quite match the actor's, and in 3D prints it's clearly a little too far away from their body.