Wheel well liner
 

I was looking at the liners in my rear wheel wells in my 2017 and noticed that they are partially held in by plastic wing nuts. Every one of mine was loose and one about to fall off. I just tighented them up by hand and will keep an eye on them.

For info, the car has about 1600 miles on it. I don’t know if they were not tight from the factory, or loosened with driving, but I will be keeping an eye on them.