Revealing mistake: Any time when the two girls are in hell's corridors and running around, you see these corridors as stone walls, yet whenever they back up against one of these walls, you can clearly see they are merely rubber sheeting overlayed on a framework as the rubber sheeting bends and contracts very clearly.
Revealing mistake: When we see Julia in Channard's house, she is dripping blood, as she is skinless. From where she is standing, she would have had to walk across the room, dripping blood, but the carpet is very clean, excluding the area where she is standing. (00:34:35)
Revealing mistake: When the Cenobites appear in Dr. Channard's office, the curtains are ripped away from the window. You can see the string that rips them away. (00:52:00)
Revealing mistake: Several of the bodies hanging from the rafters in Channard's house that Julia had killed were obviously mannequins. Real dead bodies would hang heavily and slack from their bonds but at least two that I could make out weren't weighing on their ropes at all; they were posed, standing dummies. (00:45:05)
Revealing mistake: When Pinhead becomes human again and gets his throat slashed, you can see the black net-material behind the fake skin that provided the blood.
Revealing mistake: When Frank grabs Kirsty when she finds him in the hell room, he grabs her and throws her into the stone wall. As she is thrown into the wall it bends like rubber and buckles under the impact.
Revealing mistake: When Kyle goes into the dead-body room, there is a shadow of a hanging dead person on the wall next to him. The shadow of the open door on the wall on the other side of him shows that the shadow of the body shouldn't have been there as the light would have to have been coming from the very far wall. When Kyle is looking around you can see that the only light source is the high windows on the left side of the room.
Revealing mistake: When Kirsty is confronted by the Cenobite doctor, Dr. Channard, there is a huge gust blowing towards her. If you look behind her, there is a suppossed stone wall, which appears to be flapping in the wind, revealing it is merely a fake set wall.
Revealing mistake: In the scene where Kirstie is in Hell searching for her father, she is running up and down Hell's corridor's, becomes winded and stops. As she does so, she slaps herself against a concrete corridor wall; when she does this, you can see that the "concrete" wall looks more like a rubber covering, as it moves with her. (01:01:50)
Revealing mistake: When Julia takes the cigarette from the doctor in the room with the mirror, you can see, if you look closely, that there is no blood on the cigarette. But, the hand she has the cigarette in left some blood on the hand of the doctor. (00:36:10)
Revealing mistake: When Julia first emerges from the mattress and is scrabbling on the floor, you can see the body double is actually wearing a thong. (00:30:35)