Our 2004 Southwind has had the same wallpaper issues as you are having since it was a baby, as well as foggy windows, and other stuff. A dealer in Houston replaced an entire wall of wallpaper, and yep, it began peeling, buckling, separating, too. Other areas also are coming off the walls. I just live with it for now. I may find a good wallpaper hanger to give it a go later.
Fooey on motorhome warranties because, well, there's always something else going wrong. Houses aren't really meant to move down highways, so I just consider it a part of the hobby. Otherwise I'd be mad all the time!