Continuity mistake: In the scene where Pinhead is in the church, he stands behind the table, and the candle to the right of him is straight. He then pushes the cross off the front, look at the candle, it is now on a slant then in a split second the candle is straight again as if it had never been touched.
Continuity mistake: At the end of the film Pinhead tricks Joey into giving him the puzzle box by posing as her dead father. As soon as she hands the box over he takes a knife (or sickle or whatever it is) from his belt with his left hand and poises to strike. Then it cuts to a shot from behind and he's now gripping the knife with his right hand.