Other mistake: The killer leaves the corpses of the Dean and Parker where they are and walks away, but they later appear in the room at Stanley Hall.
Plot hole: At the end of the film, Brenda could not know that Nat and Paul were to drive the truck in order to wait inside it for them.
Suggested correction: Didn't Nat come there in that truck? And assuming the truck wasn't locked or lockpicking is amongst Brenda's veritable arsenal of skills, maybe she hid by the car until she saw them coming, and got in.
Plot hole: Brenda's shown to have survived at the end and is at a different college. This is never explained given she got shot, fell out a window, thrown through a car window and off a bridge into a river.
Suggested correction: Supposedly human killers surviving the impossible is a staple of slasher movies, though that doesn't really make this not a mistake. But people in real life have survived worse.
Suggested correction: That is because the killer is moving around the bodies. Just like when Damon is killed. His body is not where it was left when Alicia Witt comes back with the cops.