What a classic
"latent design defect" Airstream has foisted upon both of you, and other owners of similar units!
An
entirely shoddy construction detail, which could be reasonably foreseen to fail at some point. Burying such a defect so deeply, that the eventual failure would likely take more than 2 years to unfold, does not absolve a manufacturer of liability.
Lucky for Airstream that no one was injured by putting their full weight on that floor, only to have the flimsy support system fail catastrophically!
AS should cover this work under warranty IMO, even after the standard warranty period.