[Patrick Wang]

You should know that a sudden shift from full forward to full reverse under load on many transmissions causes a HUGE and sudden current draw. (In Excess of 100 amps for each motor for a brief period of time) This sudden draw is enough to cause the terminal voltage of your battery to drop low enough to reset your controller.

Best advice is to not drive that aggressively. This has been our solution to that problem, we encountered it last year in the tug-of-wars.