The goof items below may give away important plot points.
When Maria is being chased by the garbage truck, she drops her stuff in the middle of the road. After Angela kills Maria and stuffs her body into the garbage crusher, Angela suddenly has Maria's stuff and drops it into the crusher.
Toward the end, when all three camp members are tied up and running into the second cabin, the girl on the left trips and the guy in the middle reaches down and helps her up with his left hand. In the next shot, his hand is tied in front of him.