These trailers are constructed different than any trailer on the market. Fibreglass reinforced plywood walls, which consist of 3/4" plywood with 1/8" gelcoat on outside and a thin transparent layer of fibreglass on the inside. The wood gets wet and acts like a sponge in between the layers of fibreglass and rots. I can happen anywhere there is a "raw" edge of plywood, along the top, around windows or any opening.
I have removed the offending rotted wood on the inside in sections as large as 48" wide by 30" tall and replaced it with a "patch" of 5/8" plywood, leaving the gelcoat intact on the outside, gluing it with marine waterproof adhesive. Some dealers will do the same. The plant will not. The only thing they will do is replace the entire wall.