My grandchildren occasionally bump the glove box door with their shoe causing a slight dirt mark on the door. Nothing serious. It comes off easily with a damp cloth. No soap or cleaner. Just water. The problem is that the dark slate gray comes off on the cloth with the dirt and when the glove box dries the finish is shiny instead of the original dull finish. This seems to be limited to the glove box door.

Any ideas on why this is happening and what to do about it?