This should be handled by your insurance, as far as I'm concerned. You did not have issues with the vehicle prior to the repairs, and now you do. I would not have accepted the car back in this condition.
I had a "minor" accident repair take six months to fix, because I would not accept the car not in proper satisfactory condition.
I had a "minor" accident repair take six months to fix, because I would not accept the car not in proper satisfactory condition.