The level of Coke in the bottle on the counter in Harry's trailer changes noticeably between shots.
(at around 50 mins) Harry is bowling and rolls a ball that is clearly going to the left side of the lane (from Harry's perspective). But, in the next shot, the ball hits the pins on the right side of the number 1 pin.
Although George DiCenzo is credited onscreen as "Sergeant", he actually plays one of the drunken sailors.
At the club, when the comedian is introduced, applause is heard, but nobody on the screen in the audience is seen clapping.
Although the story is supposed to take place in Pennsylvania, Jan-Michael Vincent is filmed on a bench where behind him is a sign with the words "Wildwood, NJ" where the movie was filmed.