Just a comesurating (sp) post here. All 5 campers I have owned have all leaked in this location. The corner molding is in adaquate, (nbt wide enough on each "leg" ) and or the molding has cut into the rubber roof itself in some, so it was leaking since original assembly. The only saving grace on my current rig is that the internal frame is aluminium and not rusted. It is all repariable and you can improve it while in there. Suggest eternabond over the corner joint, under the corner molding. Also consider under that, proflex pumped into the joint.