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 most likely wouldn't live long enough to publish the photo. (01:25:00)
Suggested correction: The picture was taken from security footage at the hospital after killing the 2 employees.
It was never shown.
Plot hole: When the couple go into the woods to have sex, after they finish, the guy goes to a pond to clean up, which is not very far from where he left his girlfriend. A couple minutes later, "Jason" is about to kill her, and she screams very loudly. Despite this he doesn't hear her.
Suggested correction: 1st we don't know how far the pond is from where they had sex. 2nd you notice his hair was wet. He could have been underwater when she screamed.
Continuity mistake: Just before Junior is killed, the level of the stew Ethel is making changes from shot to shot. (00:56:00)
Suggested correction: That's because she keeps throwing vegetables and other ingredients into the pot.
Other mistake: It seems unlikely that the police would have let Tommy keep Roy's hockey mask, as it's evidence.
Suggested correction: Already listed and corrected. It is possible that it was actually Tommy's dream.