It looks to me that there is about a 2 in uniform delamination around the 90 degree corner joint. Glue failure usually does not bubble like that so it looks to me like water intrusion. 90 degree corners do not transition the load as well as radius corners that is why you see molded front and rear caps on better built RV's. Having said that I would not hesitate to buy that MH for the right price and fix it. That corner molding is easy to remove the any loose or expanded luan can be removed with a putty knife and the exterior skin re bonded with either epoxy or polyurethane adhesive. It is probably less than a days job.