Do both motors run ok both forward and backwards hooking them direct to battery? It may be a ESC compatibility issue with the radio. You should be able to switch the Vantec from one stick drive to two stick control, not sure exactly how its done on the Vantec. With the Sabertooth its a simple DIP switch. Curious to see if that fixes it. Your speed controller is pretty old - it could be having trouble processing/interpreting the single stick inputs, but that seems like a stretch.
Ideally you want to isolate the receiver and antenna wires from motors - wood should help.
Not sure what the rating is on the IBU, but it sounds like Gary got it to work on the Hetzer. If you have the IBU2 or 3 - I would say try that before buying a Sabertooth. The Sabertooth is only a 2 motor controller, nothing else (ie not a multifunction controller). The IBU may be better /easier to integrate and get other features working (sound, gun traverse etc) as well as control the tracks.
Last edited by RC_BobM; 09-05-2018 at 09:58 PM.