I have a ML 320 Mercedes 2000. I realize it is very old but has anyone else experienced these curled covers on the rear bumper (eg. plastic plate to cover towing area)? The vehicle is in excellent condition as far as the rest of the body and performance. Can they be replaced reasonably and what can I do to avoid this issue again? I have had my car undercoated since the beginning. Would this cause a deterioration of the plastic material?