Other mistake: The Verbal Morality Code seems to be applied in an almost haphazard fashion. Several times throughout the movie, both Spartan and Phoenix swear, and do so near an area where they should be vocally reminded of breaking the code, in fact have been previously reminded, and in spite of them not moving from that location are not warned again in the face of repeated swearing.
Other mistake: As Phoenix starts to say, "Spartan? John Spartan? They'll let anyone into this century," you can see the podium Phoenix is ducking behind shift to one side unnaturally, indicating an editing error.
Revealing mistake: During the slo-mo portion of the fight between Spartan and Phoenix, Snipes intentionally slowed down his movements to allow Stallone more time to smash the glass tube; this is not consistent with the other fights in the film where Snipes was always quicker with his actions.
Answer: I'm assuming you're referring to when Simon says "Damn, I'm possessed!" He was hacking the machine when he said it, perhaps he'd corrupted the program or shut off the microphone as a side effect?
Grumpy Scot