First. This site is primarily concerned with molded fiberglass. Where the shell and the structure is all fiberglass. The construction of our trailers is more like a fiberglass boat than anything else.
I believe the trailer you're talking about is made of panels that fiberboard inside a fiberglass sandwich. Delamination occurs when water gets into the fiberboard and it starts to swell. I don't know of any good fix. There may be a fix, but I'm not sure how trust worthy the fix would be.
You might get a better answer here
. That's the Keystone Forum.
Good luck, I hope you find the answers you need.