Maybe removing it and checking the mounting points for damage could reveal the cause. My old mk2 had the same problem on the rear bumper, I left it alone as it was secure, just not straight and flush with he rest of the body.
As for repairing a scuffed bumper, I assume it's the black unpainted plastic that's damaged? Not sure if using some very find sandpaper and back-to-black polish after would clean it up?