Goofs

When Jill offers Mervo coffee, he is standing closer to her than he was before and it's clearly a separate shot.

When Scott is hit by a bat, it's clearly not a continuous shot like it's supposed to be and the cut is obvious.

Jill is being chased during the night, but when she is saved soon after that at the end of the movie, it's already day. This is because the movie was filmed during one day and one night.

When Jill is taking the shower, we see a hand turn a valve off (presumably the cold water), which causes the shower to get steamy. The hand is actually opening the valve, not closing it.

When Jill and Sarah are talking about Scott on bed, they imply penis is a muscle. Penis isn't a muscle.

A blood pack can be glimpsed on Sarah's back when her throat is cut open while hanging upside down in the barn.

Blood obviously being sprayed from some kind of a container offscreen into hay when Sarah is supposedly bleeding.

Sarah dies too soon. Even with slit throat, she wouldn't die that quickly as if she was turned off like a machine.

When victims are seen hanging dead at the end of the movie, they are clearly alive and moving.

When Jill is running away from the killer, screams were clearly added in editing over her mouth being open to make it seem she is screaming, but she actually isn't.

He rips apart Sarah's trousers too easily even though he is using a knife. They were probably damaged offscreen to be ripped that easily.

There was no reason for Sarah not to run into the house when she spotted the killer. It was closer to her and safer since she could lock the door.