Other mistake: After the T-X is hit by a truck, her primary weapon is damaged and she is seeking a replacement. As she is cycling through available weapons, dummy text is below the weapon name. The text reads: "TEXT regarding the current weapon is being displayed in XP040 weapon sub-window. Important information regarding this weapon is being displayed here." (00:59:52)
Revealing mistake: When the Terminator, Kate, and John are escaping the cemetery, they come down a winding road and drive in front of the camera in a hearse. Both Kate and the Terminator have been replaced by stunt drivers.
Audio problem: When Arnold makes the slow turn at the cemetery from Dr. Silberman's view, he starts firing his weapon at the police but we don't hear it. In the very next shot, he repeats the same action but we hear it this time.
Audio problem: When the T-X steals the car in the beginning, she's driving with both hands on the steering wheel. The car appears to be a 2001-2003 Lexus SC which has a 5-speed automatic transmission (without steering-mounted paddle shifters). However, the sound from the transmission indicates it's a manual transmission rather than an automatic transmission. Therefore, she cannot be shifting gears while having both hands on the steering wheel. (00:07:15)
Continuity mistake: Just before both Terminators are thrown in the bathroom, the T-850 grabs the T-X by the shoulders, but in the next shot it's by the arm.
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-fiveĀ°." Later, when flying the plane, Kate says aloud "all right, oh-one-fiveĀ°, 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)
Continuity mistake: After Kate's dad gets shot at the base the blood and the wounds and the holes in his jacket disappear.
Continuity mistake: When John and Kate are in the Crystal peak bunker, T-X smashes through with a helicopter, and there is an external shot of the chopper's rear blade spinning, but when T-X exits, the rear blade is gone, then in the wide shot of T-X it reappears. (01:32:35)
Answer: He was originally in talks - and by some reports, did appear on set for some period of time. While factual answers are in short supply (for obvious reasons), there appears to be a connection to his drug-use habits. For instance, he was checked into a hospital (LA Cedars Sinai) for what friends feared was a drug overdose in April 2001, and has been in and out of rehab over the years. Chances are the production company was unable or unwilling to get completion insurance.
Rooster of Doom