It's not water, I know that much. The roof was done just before the new sidewall was done on the other side. Plus, this IS Arizona... water doesn't live very long here, and it only got this bad in the last couple of months.
The other side actually had just one spot of delam, and it was dry when we ripped the wall off, but I'm sure it would have been just as bad as this side had the sidewall damage not gotten the whole wall replaced.
The slide's end panels are still good, fwiw.
If I had a building to put the trailer in, I know enough from the other side to do this side myself... with help of course. It took twelve people to do it last time. Downside is having to drive to Oregon for the panel. Although given the thin section above the slide, I'd be tempted to section it into 15' sections -- one for the front, one for the rear, and then a strip for over the slide-out. You should have seen the trailer we had to build to haul the 40' length.
Meanwhile... I just went outside with a stepladder. Definitely no water behind any of it. But the really bad news is the sidewall behind the slide-out, which isn't as visible in the photo, looks like it's on the verge of delaminating too. Lots of little 1" or so bubbles starting to appear. I'm not sure it's even worth repairing. The whole sidewall will HAVE to be done. Gee, thanks again Keystone.
I emailed the guy with the repair shop who did the other side... he's since moved his business to Montana, so we'll see how things go.
