If it isn't something you can fix with your steering trim buttons(check them on your controller) and if they turn all the way left and don't move you may have a loose wire connection to your steering potentiometer. It controls how far left and right your wheels travel and if one is loose it may think that it's centered (but obviously isn't.)

If it is loose, you may want to see about getting it fixed if you can't find a replacement from RS.