Continuity mistake: Van Ryberg shoots a grenade, which goes in at an angle from the right of the screen to the left and hits the robot on its right side. Van Ryberg fires another grenade, and this time the grenade travels from the left side of the screen to the right hitting the left side of the robot. The problem is, Van Ryberg didn't move and shot both grenades from the same place, it would be physically impossible for him have hit the robot from both the angles depicted onscreen.
Continuity mistake: When the NSA guys are taking the Doctor through the military base, in one camera shot they slow down and there's a metal globe ornament on the side of the road. The next camera shot to show outside the car shows them to be fast moving. The next camera shot shows them slowing down again at the same metal globe ornament.
Continuity mistake: Van Ryberg, the Doctor and Madison get picked up in an old Chrysler people carrier, which is distinctly square shaped and with silver alloy wheels. When they get to their destination however, the people carrier has now changed into a Chrysler Voyager with a much more rounded body, and now sporting black steel wheels.
Continuity mistake: When the girl is shot by the robot in between the two yellow diggers, the laser leaves a big red blood patch on her top, but when we later see her dead body on the ground, the big patch has disappeared.
Continuity mistake: When the Sheriff and the two people in the police car get rescued in another black SUV, the license plate changes from when they are picked up to when the stop at the base.
Continuity mistake: When the machines start falling out the sky, Van Ryberg and Madison start running away, and if you look on the horizon as they are running, it's all flat ground. However, in the next shot of the machine rising out of the ground, there is now a massive hill in the background that wasn't there in the previous shot.
Continuity mistake: When the black SUV transmorphs into a robot, it goes to destroy the police car. The CGI interpretation of the police car looks absolutely nothing like the real car, the front grille for instance being completely oversized, and the wheels change totally.