Corrected entry: It is never explained how Jason appears at the beginning of the film in his normal hulking form since the end of the previous film showed him being washed away from toxic waste in the sewers of New York City and turning into a little boy.
Correction: This movie was made as if the previous movie didn't exist. Just ignored it altogether.
Corrected entry: When Joey is punched in the face by Jason, she starts falling forward, but in the next shot, she's turned around and falling in another direction.
Corrected entry: At the end of the movie the demons pull Jason down and he is tightly wearing his mask, but the next shot is his mask laying on the ground that Freddy comes back up to get.
Correction: It is on purpose to create the tension for the Freddy vs. Jason movie because it is Freddy's glove that pulls Jason's mask under and it might have been discarded by the demons.
Corrected entry: When Jason is lured into the trap by the lady cop, he is encircled by a SWAT team, who promptly open fire. If they're in a circle around him, how come none of the cops get shot?
Correction: Because they're not amateurs. All the gunmen are laying down, firing UP at Jason head-on, so the only way one of them would hit another member is if he aimed all the way DOWN and to the SIDE, which is highly unlikely, since these guys are SWAT, and it's very a exclusive team. you must have impeccable aim and 20/20 vision (and most importantly, a little common sense).
Correction: The boy was another of Rennie's hallucinations. Jason awoke presumably after the toxic waste dried out the next day and retrieved his slightly melted mask then made his way back to Crystal Lake. The mask he has belonged to Jim Miller, who he took the mask from in part 8, as his other one was destroyed by Tina Shepard in part 7. Why there was an axe mark in Jim Miller's mask is anyone's guess. Probably authenticity, as it was national news that Jason Voorhees wore a hockey mask. Also, the writer/director of Friday the 13th Part VIII: Jason Takes Manhattan has stated on DVD documentaries and in books that he wanted to portray Jason Voorhees as more of a supernatural spiritual entity rather then just a walking corpse. Rennie's "visions" were more than just her own hallucinations because her dog saw one of them earlier on in the film.