VEX ?

[EricH]

I'd also go with too much current. Your FRC robot would probably act the same way if the breakers were tripping, though with a bunch of audible snaps.

Quick test: Pick the robot up off the floor. Run it. If it keeps going, you should re-gear--you're drawing a lot of current when it's on the floor. If it exhibits the same behavior when it's off the ground, check for binding or debris in the drivetrain. If everything is clear, check code.

It could also be that the motors are trying to fight each other, though that would be more likely to stop the robot altogether.

I don't think it's communication; tethering and wireless are both bad. I also don't think it's binding; while that could be an issue, it would be most likely to happen at the same place every time.