Your Sherman Control Unit is intended for a front wheel drive tank. You have it installed in a rear wheel drive tank. Seems you would have needed to swap leads (right to left side) on the motors and reverse your throttle direction to make it function properly, maybe it has something to do with what you did to correct for the change from front to rear drive in your transmitter.

If I were to obtain one of those WSN / Trumpeter T-34s I would put KV DMD/MF units in it. I don't see that happening any time soon though.