Revealing mistake: The two workers to the right of the entrance are fake digging. Their picks never touch the ground. (00:27:20)
Revealing mistake: After the power goes out at Sarah's hospital, she lights a candle. While she's walking along with it, it's obvious it's not made of wax. It looks like it's made out of plaster.
Revealing mistake: When entering the tomb there are quite a lot of shadows on the walls and statues. We are supposed to be in a sealed tomb. Where is all the light coming from? You can tell by the shadows that light is coming from multiple locations, not just the priest's lamp.
Answer: Weapons on statues in conventional churches point upwards in veneration. The weapons here are pointing downwards in an offensive gesture.