Could be a problem with your steering servo. Take the top cover off the front end and see if there is lint or debris blocking the servo arm or the tierod.
The steering servo is not returning to center so... I guess you could tear apart the servo and so what's doing in there. Or using the 90 day warranty might be a good alternative.
My original xmod had this problem. If you are handy with a small tip soldering iron you can probably fix it but if not I would return it to RS. The problem on mine was a poor solder connection from the servo to the rx board on the bottom of the car. It required total disassembly of the car.
I have a similar problem with one of my cars. The steering servo seems to be binding up at one particular place. I have the servo apart and can't see anything wrong with it, however. It is definitely something in the gears, as you can feel it bind up if you move the servo horn by hand.
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