Continuity mistake: When Pnub's head is picked off the kitchen table at the end of the hand-cutting scene, the ring of blood that formed around Pnub's neck stump is joined with the larger pool of blood that it came from. When Pnub and Mick come back to the kitchen later on, the ring is no longer attached to the larger pool. Blood does not evaporate like that when it dries.
Factual error: When the bloke's head gets cut off in the beginning by the circular saw blade being thrown, surely there would be more blood, like when his mom got killed under the bed?
Continuity mistake: The cheesy puffs that are thrown to the decapitated head in the chair change from scene to scene.
Visible crew/equipment: When the mom goes downstairs to see what the sound is, she slips on blood and falls on the floor. When she starts to stand back up, you can see her knee pads.
Continuity mistake: When Anton is going to the dance and is backing out of the driveway in the pickup truck, you can see both of his hands on the wheel. This is after he has cut his hand off.