The door above the passenger taillight might give you access to the inside of the wall near the lower bubble to check for moisture / rot damage without too much disassembly.
ETA: For a quick check you could also pull the jack mount screw closest to the lower bubble. If it has started to rust, is still wet... you know what to expect...
ETA2: The bathroom is in that corner, right? In theory, a potential leak source could be internal; although I can't really imagine how or where this might happen so far up and on that wall.
There is no point trying to re-glue the delamination until you know the root cause. In the likely event of a water leak, the leak needs to be found and sealed, and the wall needs to be dry. Any rot damage that is not just cosmetic needs to be fixed. I agree that you should contact the mfg; potentially swing by the factory for repairs if you can rearrange your travel plans.