Luan woes

I'm not sure if I am posting in the right forum or not, so I apologize in advance. My topic kind of fits a few places I suppose. Long story short, my 2017 Keystone Sprinter 33bh has water damage. I noticed it on our trip from Florida to Wisconsin last summer. About a 4 inch by 6 foot strip right in front of the slide out seems like nothing is there except linoleum. Very odd - it is a high traffic area and I never once noticed softness, just one day it was like a chunk 'fell off'. I took it in and it was estimated a little under $9K to repair. This is, of course, a near-full disassembly and inspection. I have comprehensive coverage on it (not sure I can drop company names here), so I am in the midst of a claim. I have maintenance records that show the roof seals are not in need to repair. Insurance company feels that the seals around the slide are to blame. I feel like it is environmental - we have traveled a lot with it, and lived in Florida for 4 years. We've been through storms and lots of weather, both on the road and at sites. Never had an internal water leak that I can recall. Insurance has been hemming and hawing for about a week on it. Calling back and forth and such. What are my chances of having this claim honored do you think? Anything I can do to help my chances? I guess on a positive note, they are entertaining the idea of covering me and didn't laugh me out of the conversation for mentioning it. On a related note, I am preparing for the worst and doing the job myself. I can tap on the bottom of the membrane below the camper and can tell that something is bouncing around under there - bits and pieces of flooring. I have done flooring work with plywood - any tips or tricks with deteriorated Luan / sandwich board that they use in there? I assume that I can just replace the bad pieces of Luan with marine plywood or something similar in the right thickness.