Deliberate mistake: There is just too much movement and detail in the synthetic skin masks. Peyton lost a large portion of his face in the explosion, and cannot make much expression with his own face, but somehow he can make the masks move perfectly just like a real face.
Deliberate mistake: When King Willie is confronted by the Predator in the alley the Predator approaches him cloaked stepping through the puddle of water. You can see his footsteps causing the water to splash up. However, you can see the water splash up and go through his foot. The Predator is only cloaked, not intangible so the water should have splashed upon his foot, not go through. Water against his foot would be visible too, even though he is cloaked. (00:47:45)
Deliberate mistake: It would be impossible for anyone to push up on a casket lid six feet underground and make the lid move much less crack enough to get their whole body through, the dirt would fill the box and trap the occupant.
Deliberate mistake: The elevator operated by gremlins starts ascending at around 5 stories per second, based on the floor readings. Yet when the elevator suddenly stops dead, Kate does not fly into the air caused by the huge speed change. (00:50:05)
Deliberate mistake: When Andy opens the tap to the liquid plastic it is that some of the liquid squirts on his hand. That would hurt and stain, but Andy doesn't seem to care... (01:14:35)
Deliberate mistake: In the whole of the 'Psycho' series, there has never been a closet door next to the dress cabinet in Mother's room, but for this movie there is suddenly a closet.
Deliberate mistake: After Ryan and Michelle finish changing the flat tire and are surprised by Leatherface, he chases Ryan around the back of the car and smashes the windshield. At the moment the camera is in the backseat shooting out, we see the chainsaw with the chain popped off and hanging. My best guess is that it was done intentionally (for safety reasons) because the saw was close to Ryan. The crew must've been too lazy to completely remove the chain and just popped it off the track instead. (00:25:25)