The rubber stoppers can be retracted by turning clockwise, and extended by turning anti-clockwise. If they extend too far they force the plastic paint protectors to distort and move.
Just checked my 14 day old
MCS and the plastic has started to move, and the stoppers were out too far. Have now retracted them to the maximum. No sign of paint damage though.
I'll wait a few days and see what happens, and also listen to hear if the tailgate rattles. Then I will replace the plastic with something better !