Continuity mistake: During Frank's second visit to Stephanie's home the stack of pancakes J5 is holding decreases from a load to a few over several shots.
Continuity mistake: At the beginning of the movie when the "Red Army" approaches, the tank has his barrel locked in a transportation brace. As soon as the tank fires back, the brace is gone.
Continuity mistake: In the scene right after Number 5 almost drives the snack wagon into the lake and the Nova guys are shooting him, you clearly see him get shot in the hydraulic pistons which control his head motions. Yet, in the next scene (in the truck) Number 5 comfortably moves his head.