Continuity mistake: When Ash is beating his dead ex-girlfriend with the plank, you can see the plank start to split in half; in the next shot, it's back to its original form. (01:05:25)
Deliberate mistake: When they are listening to the tape, Cheryl yells out and shuts it off. Scott says he wants to hear the rest of it, but then deliberately fast-forwards it a bit before starting it playing. If he wanted to hear the rest of it, why does he skip part of it? This allowed Cheryl to shut it off as soon as she finished her line/action, but then Scott could fast-forward it past a mark on the visible reel-to-reel tape so it would start immediately on the chanting rather than in the middle of the lecture where Cheryl stopped it.
Continuity mistake: Just after Ash has defeated the demons by throwing the book into the fire, he realises that it is dawn, if you look outside the window it is really bright outside yet when he actually steps out of the cabin, the sky is orange as the sun is just rising. (01:22:00)
Revealing mistake: When Ash is about to gouge out Scotty's eyes, you can see there are already holes in the eyes before he does it.
Continuity mistake: When Scotty stabs Shelley in the back with the sword, she falls and lands on her back, which should have impaled her, but when she's on the ground the sword is nowhere to be seen.
Continuity mistake: When Scotty swerves from the truck in the beginning, Ash is standing up behind him, with his head halfway out of the car, yelling at him to turn the wheel. In the next shot both window are up again. It is just seconds before Scotty honks at the fishermen.
Continuity mistake: When Shelly is possessed, she and Scotty fight and she amputates her own right hand before she goes down. Moments later, she comes back to life and Scotty starts dismembering her with an axe, starting with her left hand. We plainly see the axe come down full-force on her left wrist. However, in two subsequent shots, we see her intact left arm and hand in the foreground, reaching for Scotty as he continues chopping.
Continuity mistake: When he is in front of the movie projector, the blood starts dripping, it flashes from back and forth, looking at the projector and the projection over Ash. The blood is dripping in spots all over the lens, but when you look on the wall, its dripping from the top. (01:10:15)
Continuity mistake: When Scotty stabs Shelley in the back with the ancient sword, the wide shot shows him with his arm around her holding the sword. In the next shot, his arm is no longer around Shelley.
Continuity mistake: Scotty's shirt changes a bunch of times. His normal shirt is blue-and-white plaid, but when he's in the cellar with Ash, close-ups of him dismembering Evil Shelly, and outside after he and Ash have buried the bits of Evil Shelly, it's a plaid that's mostly red with a little yellow and blue. At the end, when Evil Scotty is in claymation, his plaid is mostly yellow with small red and blue stripes. (00:47:25 - 01:19:25)
Audio problem: In the beginning when the group is driving to the cabin the sound of the car mysteriously cuts out. You can hear branches breaking but you can tell they are dubbed because the car drags a large bush behind it with no noise. (00:03:50)