[Alan Anderson]

If you're using a four-motor drive system, you might have two of them swapped so they're fighting each other during an attempted turn. This could perhaps end up pulling the battery voltage low enough to disable the PWM outputs but still not trip the Jaguars' own low-voltage detection. Try taking out all of the drive motors' circuit breakers and put them back in one at a time to verify that each motor does what you expect it to.