To be clear, my 2013 Forest River XLR 300x12 came with a ramp door made by Lippert. My door had to be replaced because it was failing at the hinge line. I first noticed the damage when it appeared that the inside covering was bubbling up. The door felt spongy in that area. Lippert determined that my door failed from water damage. Water was able to get into the door because the driver's side aluminum edge trim was loose (unglued?") on the door. Lippert replaced my door, even though I was out of my warranty period. My new door came with a bead of sealant where the trim rails meet the outside of the door. I can also see evidence that much more glue was used to attach the trim rails to the core of the door.
I thought that the door design contributed to the failure. I think the hinges should be longer, or the door should be re-enforced at the hinge line. One thing that I notice is that there is flex in the new door when it is opened. I can see and feel this at the corner seam of the outside trim rails. I am thinking about how I might make something that would spread the load of the hinges (and the hinge springs) across a larger area of the door.