Other mistake: In the scene in which the T-1000 arrives at Dyson's home, he sees the files burning in the trash can. We know this is happening as the others are in the Cyberdyne building as the police radio, just a few moments afterwards, calls all officers to the area. There is unburned paper on top of the pile. Given all of the time that they were in the Cyberdyne building, there should have been a large amount of ash in the trash can. There was no sign of strong wind to have blown the amount that should have been present. There is an incredibly small amount of ash in the can when it is shown, it just isn't possible with the elapsed time. (01:44:00)
Continuity mistake: When the Terminator smashes the driver's window of the blue station wagon, there is a large section of glass at the top of the door that is stuck in the runner of the door. In the next shot as the Terminator is closing the door, this same section of glass is now missing. Not enough time has passed in the shots for it to disappear and there's no sound of it dropping. (01:13:25)
Other mistake: When Lewis looks at the cup that he got from the coffee machine, the cup has two Jacks and two Aces. When he looks at the bottom of the cup, it has a Queen underneath giving him two pairs, but he tells Gwen the receptionist that he got a full house.
Revealing mistake: When the T-800 is reloading his shotgun in the alley with John, he reaches into his pocket, presumably to grab shells for the shotgun. In the shot with him and John in frame, his hand comes out of his pocket empty, but we hear him load another shell into the gun in the next shot.
Continuity mistake: When the helicopter smashes into the back of the police van the front gets completely smashed in and crumples. Next shot is from the side - the helicopter falls to the ground and the front is intact, then smashes to pieces on impact.
Continuity mistake: When Sarah uses her shotgun to shoot the T-1000 in the eye, the first camera angle reveals that the shot has disfigured his head forcing the tissue around the eye to be pushed outwards as a result. In the next shot, when we can see Sarah through the hole as it 'heals', we can see that the head is already in its regular shape as the hole fills.
Audio problem: In the scene where John is running away from the T-1000 in the corridor of the mall, one of the curators shouts out "Hey!" The Terminator appears in scene so John runs back the other way passing the same curator he ran past before who then shouts out "Hey!" at him again. The curator's mouth never moves during both of his lines.