Other mistake: When Jason is in the corn field during the rave, after Jason breaks the guys neck, the other guy burns him with a torch and the flames burns around his neck area, which should have caused him to not have any hair. But throughout the movie, his hair is still there.
Other mistake: Jason drowned in 1957 yet Stubbs says he drowned in the 1930's.
Suggested correction: Stubbs actually mentions that Jason drowned in 1957. He said it while he was talking to the teens at the table.
Other mistake: When Will and Lori get out of the Lake at the end, Lori's arm isn't burned. It's only scratched.