Problem with old bot

[kinganu123]

lol, sorry about that guys. Once again I had sent a freshman to do research, and I can almost guarantee you that they didn't search before posting (with my account).
But basically, we stripped the good 'ole 2010 robot and basically left the 4 CIM motors, the 4 mecanum wheels, the PD board, the cRIO, and the DS. It's all mounted on wood and the other parts (such as relays) are still mounted, just not connected to anything.
That being said, we can go forward, left, right, and spin properly, but once we go backward, the bot essentially stops working. I expected it to be motorsafety to be throwing it off, but alas, the freshman didn't do enough asking or researching and they assumed it to be electrical, because 224's programmers are never wrong XD. I'd also like to throw in that the joysticks and motorspeeds are programmatically correct, but i haven't had them check motorsafety yet.
However, I dare not eliminate electrical as the problem YET. I will make note to them to make sure that the robot is properly grounded.
Are there any other suggestions?
Thanks