Continuity mistake: During the final chase scene where Melanie Kinnamin is running through the woods the pink sweater which is over her shoulders disappears and reappears at random, until she finally loses it by the tree where her co-worker is found murdered.
Plot hole: When the cop shows Pam the newspaper clippings they include what look to be fresh photos of the real Jason from the events of Part IV, yet no photographer is ever seen taking pictures of Jason alive in the previous films and well and most likely wouldn't live long enough to publish the photo.
Plot hole: At the end when Tommy is in the hospital, he gets out of bed and goes over to the drawer where his belongings are. He opens the drawer and there's the mask the killer was wearing. How did it get there? The police would take that as evidence. There is no way that police would let Tommy keep this mask for a souvenir.
Revealing mistake: When Reggie hits Roy with the tractor, the wound on his chest only appears after he has hit the ground.
Continuity mistake: Just before Junior is killed, the level of the stew Ethel is making changes from shot to shot.
Continuity mistake: After Reggie's grandfather flies through the window, his head changes positions between shots.