I haven't seen this kind of "damage" (except in pictures) but maybe can explain how it could happen. Essentially, the adhesive (which can be damaged by moisture and heat/steam) actually comes apart, separating the bond, which allows the FILON sheeting to return to it's "manufactured and/or stored structural condition". In other words, with enough "steam" applied to the surface over a "long enough time" will cause the adhesive to "lose its bond" (separate) and the steam "softens the FILON" allowing it to return to the "rolled condition" in which it was stored before assembly.
Now the long explanation, so bear with me: FILON is less than 1/8" thick (about 1/16" to 3/32") and comes in a 8' wide roll. The roll can be up to 200' long, weigh several thousand pounds and are 4 or 5' in diameter. As the FILON is used, the roll gets smaller and smaller. The last part of the roll is "curled much tighter" than the first part of the roll. While FILON isn't supposed to have "memory" if the roll has been stored for a long time, there's going to be some "spring-back" to the FILON and it won't lay flat.
On the sidewalls of the trailer, a "vacuum-bonding" process is used to create a "solid wall" structure that consists of an outer layer of FILON, bonded to a single (or double) layer of luan, bonded to 2" of foam/aluminum studding, bonded to a single layer of luan that's bonded to the inner wall that has vinyl wallcovering (wallpaper). This entire structure is placed in a vacuum and heavy rollers are used to "force the bond" making it a single structure.
On the rear wall, that process isn't used. The rear wall is a "free hanging wall" and is a necessary part of the structure because it's the way the wiring is routed from the floor/basement to the ceiling/attic as well as how the tail lights, clearance lights and often other wiring is routed. So the FILON is bonded to either a single layer of luan or sometimes bonded to a paperboard type of material. This isn't done using the same process as the sidewalls but is bonded using a "contact cement" bonding process where the adhesive is applied to both sides, then once almost dry, they are mated and the bond occurs. After that structure is created, it is "hung in place" on the trailer and secured "only with screws under the edge molding and around windows and lights. That gives the "clean surface, free of screws" that moves slightly when pressed with fingers.
Now, herein comes the problem. The adhesive, like the boat deck that Cqyqte talked about in the above post, can separate under extreme conditions. His was a cover on his boat that held water which turned into steam when the sun hit it, probably causing the "steam damage" to his fiberglass decking. The same can (might not in all situations, but can, if the right conditions exist) happen to an RV that's stored under a cover that doesn't breath properly and allows moisture to remain under the cover. This isn't likely to occur in every RV because those with back walls that were constructed from the "outer coils" of that big FILON roll weren't rolled as tightly as those back walls that were constructed from the inner (tighter rolled) coils of that big FILON roll. As the FILON is heated by the steam, it tends to return to its storage position, causing it to apply pressure to the adhesive, pulling it away from the backing board. Keep in mind that if a "paper based" backing was used, as it gets wet, it loses rigidity and can't hold the FILON in position, making the moisture problem even worse. The FILON has little "structural strength" (the reason a backing board is used) and will pull through the screws or staples as it separates from the adhesive.
Just as every laminate flooring company has a caution to not use a steam mop on their flooring because the moisture will penetrate the outer flooring and cause the "paper backing" to swell and damage the floor, using "steam produced under a cover that holds moisture" on an RV can cause damage (in some situations as described above), not in every RV, but in some, depending on the adhesive used, the "tightness of the FILON coil" and the conditions during storage under the cover. These are things that the average RV owner will never know, until the situation occurs and he becomes the "victim of a perfect storm".
I can say that this year and last year I've seen more pictures on the fourm showing FILON damage, water intrusion and now wall separation than in the past. I don't know if it's a sign of things to come, a change in materials used a few years ago (most of the trailers are a 2, 3 or 4 years old) or if it's the type of covers being used during an especially warmer and wetter winter than usual. But, I'm guessing we'll see more and more of this kind of problem, likely because we've got more and more RV's in service. If we have a "hotter than usual summer" followed by another warm, wet winter with more people covering their RV, next year there will probably be even more pictures of this kind of damage.
Now, as for Keystone changing their manufacturing process or materials to prevent the problem: With more than 30,000 RV's produced annually (they produce more than that but I don't have the actual numbers) and even if 100 trailers were affected this year, that would only be a failure rate of 0.003, less than 1/3 of 1%. In manufacturing, a failure rate of less than 3% is considered acceptable. So, I wouldn't look for any "dramatic and costly" changes in production by Keystone. I know that's not what the owner of a damaged trailer wants to hear, but to the RV industry, it's probably going to be considered "acceptable casualties"......
