In the old days (pre metal studs) delam was a real problem. Water not only ruined the siding but also rotted the studs and braces. The motorhomes of today are studded with steel not wood. Delam looks bad but is not usually structurally destructive. You may not have the usual delam that was caused by a water leak that rotted the wood supporting the fiberglass. If yours seems to come and go with heat, it might be the glue letting go of the fiberglass when it gets hot. This is uncommon but has happened in the past. It is easier to repair. Water damage delams the wood backing it goes to pieces. Glue does not work well. If the glue failed you can sometimes go in at an opening (window, compartment, access door, etc) and spray new glue in the wall.
1998 Pace Arrow 35 ft. F53 Ford V10 2014 Honda CRV toad
32 years mechanic at Delta Air Lines 15 year motorhome service manager. 3 popups....2 travel trailers....5 motorhomes....loved them all.