Do a search. You will find pages of posts like yours. It is the big fender extender. They just catch to much air and pull on the bottom of the fender. I picked up a show chrome extender for my 2012. When I saw how much air it would catch and all the posts of damage, I did not put it on. No fender damage issues for me.
The Fender Extender brand may be narrow and tapered enough that it does not catch the air as much. I had one on my ST 1300 and it was nice, compact and worked great.
2012 GL 1800
1988 GL 1500
1977 GL 1000
2012 KLR 650