Problem with my tailgate and bed

Hey everyone, so I've never seen something like this. I hope my truck isn't the only one with this problem. I have about 5000 kms on my 2016 trd sport double cab and today when I went to wash the bed of my truck, I noticed the tailgate is "grinding" down the end of the bed. If that makes any sense. It's as if the vibrations while driving grind the bed together? I can't think of anything else that would cause this. When I run my fingers on it I get a white powder of plastic that's been literally grinded off. Anyways here are some pictures, my service is at 8000 kms so I will bring it up for sure.

Also note this is only on the drivers side, the passenger side is completely normal

 

Also that is fiberglass.

 

Okay thanks guys

 

Please let us know what they do at your 8000 kms service.

 

Is the tailgate level on both sides up top when closed? If so then might just need to adjust the tailgate panel a bit by loosening the torx bolts and moving it on that side a bit. Not sure how much it can move based on the type of bolts used on the panel, tho.

 

A Tailgate seal kit may work. I did that to mine but yours may be out of adjustment.