Check all the seals, mine had a leak in the seal on a cellar door that allowed rain water to leak in and it saturated the fiberglass insulation. I had to remove all the fiberglass, rebuild the floor, and, obviously, replace the cellar door seal. I used spray foam insulation instead of fiberglass, not only more water tight but also fire rated at pretty much fire proof.
2010 Zinger ZT29DS - SOLD
2021 Grand Design Reflection 315RLTS
2020 Silverado HD3500 Duramax