I have seen a similar issue with the servos on the camera. I had them connected to PWM 1 and 2, and when I accidentally discharged static to the chassis of the robot, or connected the serial cable to the program port, the servos would twitch, big time. This doesn't prove to be an issue with the tracking code, though. I have never connected anything to 13-16, though. I use 16 to power the camera. That's probably all it's good for...
I remember reading somewhere that the new master code cures a twitch, but I don't know if it's the 13-16 issue, and I haven't upgraded, so I don't know.
Good luck,
JBotAlan