We had the same problem on our 2013 36KS. Noticed it when we got back from our first long trip in winter 2013. There was a single screw holding the left front fender in place - the fiberglass broke out where the screw hole was. I repaired myself by reinforcing the area with a custom fabricated stainless steel support and a Bondo fiberglass repair kit. Now I have 2 support points for the fender and the lower edge of the fender is reinforced. Very solid.
2013 Coachmen Encounter 36KS, 2012 Honda CR-V toad, Roadmaster Falcon 2, Brake Buddy Vantage Select, Protect-a-Tow, 5 Star Tune, M4 LED lights and many other accessories & mods.