You said after a full left turn, do you think it could be the response is so fast and sensitive with your fancy new radio that when you let off the wheel it snaps back the other direction a bit? I know it is far fetched but I have seen it before. The servo traveling too far is prob more likely, but just s thought.
You want to set your steering endpoints so that you just get full travel and no more. Usually its pretty close at 100%, but its always better on your servo and servo saver to back off until there is no extra stress. Turn one way and adjust the endpoint back and forth so that you can see where the steering stops, then you will know where to set it, repeat for the other direction.