Looks expensive to fix.
I’m no expert, but I’d say the “bubbling” is more of a deamination from water leaks.
Drill holes in the delaminated areas. Inject a slow setting epoxy. Apply vacuum bagging to force the delaminated areas against the wood core.
Once that is done, fix all the water leaks that caused the delamination in the first place.
I have the same thing going on with my travel trailer. I had an RV specialist come and take a look. I live in Arizona and he said it’s delamination from the heat. He checked everything out, good news no water leaks. Mine go away in the cold. Hope this helps.
Pull the windows. Use the hole where the window was to work with epoxy such as west systems. clamp the wall back together. Use 3m 4200 to reseal the windows to the body.
You won’t have a lot of time between the pouring of epoxy and the clamping bit. Do a couple ‘dry runs’ where you practice pouring and then clamping but without using epoxy. Chunks of 2×4 or the like and plywood make for a decent press with some wood clamps. You’ll also need to get the right activator for the temperatures you’re working with.
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Watch YouTube videos on delam repair for RV walls, it’s more involved then one may think, can still be done but involved.