Revealing mistake: At the end of the movie when the missile hits and explodes on the city in the backround we see the buildings closer to the screen (the barn and the small office building) get domolished by the shockwave, but all the trees surrounding these buildings don't even move. (01:41:15)
Revealing mistake: When Arnie body slams the TX into the toilet, the fact that it's a dummy is blatantly obvious, even at full speed. (01:20:15)
Continuity mistake: When John talks to Catherine while sitting at the table in a moving RV, watch the explosives he is working on. Position of the charges changes with every shot facing Catherine. At one point they completely disappear from the table leaving only the Glock 18 handgun, and just a second later the table shown full of explosives again. (01:09:55)
Revealing mistake: In the driving scene after the first run in with the TX, the T-850 is driving the truck, John is in the passenger seat, and Kate is locked in the back. The T-850 has to cut open his abdominal area to pull out the nuclear power cell that has been damaged, and dispose of it. In the shot before he begins cutting, you see the T-850's chest is flat as it should be under his shirt. But once you see him begin cutting into his abdominal area, the top of his chest has a ridge. This is an obvious show of the prosthetic chest the actor scoot up against to be as his chest and house the fake skin, metal, and power cell for the scene.Quantom X
Other mistake: When General Brewster tells John and Kate to go to Crystal Peak, Arnie confirms its location as "52 miles north-east, bearing zero-point-five°." Later, when flying the plane, Kate says aloud "all right, oh-one-five°, 52 miles." That's a 10-degree error, for 52 miles, which would put them somewhere in the ballpark of 20-25 miles off-course. (01:17:25 - 01:29:40)David R Turner
Continuity mistake: After Kate's dad gets shot at the base the blood and the wounds and the holes in his jacket disappear.
Visible crew/equipment: In the shot just before the ambulance truck runs over Arnold's police motorcycle, you can see on the right-hand side of the screen a film/crew member truck that doesn't belong in the shot. (00:34:40)