I'm kind of surprised no one else has responded on this issue. Anyway I have pictures of what I found and how I repaired it. These photos are also posted in the gallery.
You can see how the force of the support is pulling against the screws and pulling them out of the door.
Here you can see they were obviously reattached once. This happened before delivery, I suspect at the dealer because one of the screws didn't match.
I made some plates out of stainless steel and bolted through the door. The original plates were the same size as the brackets but the force was pulling them in and distorting the gelcoat so I made these larger to give more surface area and they seem to work fine.
Forest River says they will reimburse me for making the repair. We'll see how that goes. My only expense was the SS screws which were less than $10. I made the plates out of scrap. I am going to charge for the labor at the shop rate my dealer gave me. He said that sounded fair to him. I'm anxious to see what FR says about that.