Revealing mistake: Brayker shoots The Collector through the eye with an arrow just after he's collected the key from Roach. You can see the section of the arrow shaft that sticks out the back of The Collector's head bend as his head hits the floor after he falls over the upstairs railing and crashes through the coffee table.
Revealing mistake: When The Collector cuts his hand to summon the demons, you can easily see that no actual cut is made, and blood begins to drip from a point beneath the starting point.
Revealing mistake: When the Crypt Keeper is trying to direct a film and is reprimanding the actor in the bloody suit, the reflections of the green screen around the Keeper's collar.