Continuity mistake: We see Vic outside the halfway house, just starting to chop a 4-foot log with a double-bit axe. In the same scene a few moments later, as Joey approaches, Vic has chopped about a third of the way through the log. Problem is, it's a completely different log (different shape, texture and color).
Revealing mistake: When Pete gets his throat slashed, you can plainly see that there's no actual cut, it's just a line of stage blood. (00:26:30)
Visible crew/equipment: In the film the ambulance is called to Pinehurst. When the ambulance comes to a stop the boom mike can be seen in the bottom part of the rear window. (00:21:05)
Plot hole: After Roy is knocked out of the barn doors, Pam and Reggie slowly walk over to look, but then Roy jumps up and grabs onto the barn floor. However when we see a wideshot of him dangling, you can see there are no ledges for him to have gripped onto while he fell, and that it's just a flat wall. Therefore he couldn't have popped up because there weren't any ledges for him to have grabbed a hold of on the wall. He should have instantly fallen on the tractor harrows. (01:18:45)
Continuity mistake: In the film Tommy tosses the alien mask that he wore to scare Reggie on his bed and the mask slides down the wall and is all crinkled up. In the following shots Tommy takes out another mask and you can see the alien mask now laying flat on his bed and away from the wall. (00:13:10)
Continuity mistake: In the film the killer.aka."not the real Jason" is seen walking through the rain soaked grounds and woods , but yet when he climbs up the ladder at the end of the film his shoes are pretty clean. (01:10:30)
Plot hole: When Robin goes to bed you can see that Jake is not there. When she turns over Roy couldn't possibly have put Jake there in that short time without her noticing, not to mention that she was still awake. (01:03:30)
Revealing mistake: During several of the deaths committed by the impostor, look closely. The shirt sleeves are dark green instead of the dark blue sleeves of the jumpsuit the impostor wears. Clearly Tom Morga, the hallucination of Jason, did these scenes instead of Dick Wieand, Roy Burns/impostor Jason.