Revealing mistake: When the Tall Man gets hit with one of his own spheres he moves his head a bit too much in the subsequent shot where the sphere is drilling into his skull, and thus reveals the sphere's blades are actually dull props that are covered in fake blood to make it look like they're impaled in his flesh.
Continuity mistake: When the priest is sitting in his home looking very nervous he pours himself a drink, takes a sip, then starts hearing scratching noises at the door, and the next shot shows that this door is locked with a chain lock. He then says, "Bless me mother," gets up and slowly approaches the door, but it is now shown unlocked, before he locks the door with the chain lock. (00:33:15)
Continuity mistake: Reggie and Mike are sitting by the fireplace downstairs and they decide to get out of town. Next to Reggie is a coffee mug resting on the stone ledge of the fireplace. Mike goes upstairs and is pulled through a mirror. Reggie hears the glass breaking and runs upstairs, and now the coffee mug is gone. Reggie then runs back downstairs to grab a shotgun and now his coffee mug has reappeared but is now on opposite side of the fireplace. (00:01:55)
Revealing mistake: In the mausoleum where the priest is killed, when the woman is thrown back she is too obviously on a wire. She goes up at an angle, bounces off the wall still flies up for a second. If you look very closely, you can actually see the harness stings briefly. (00:53:30)