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.
Other mistake: Newton Crosby (the programmer for the robots) is at the Vista house and Stephany is in Astoria. More than 113 miles (2 hours) away and Stephany is calling to meet up with Crosby to talk about number 5. I don't think 2 hours passed before they met up. All this happens within 5 min. Not to mention how did Crosby get out to Vista house so fast?
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.