You could delve deeper into the source, whether it's something in the gearbox or motor. I'd look over the slow side, check the lubrication, look for obvious sources of binding, check that the frame is square and that there's no rubbing anywhere, especially near the final drive shaft.

Couldn't hurt to take the tracks off to compare tension as you spin the sprockets and look for evidence of track rubbing on the hull on the offending side.

There's no reason to put up with bad steering.