David is the whole panel fabric dropping or just a small spot?
If its a small spot could try and squeeze some glue behind fabric and smooth out to 1/8" plywood behind it.
Not sure what will happen if you drop rib sections out of seams. If you have a light fixture near seam take a look with mirror from the top of one.
You could also call Newmar repair and ask their advise on how to fix. Your out of warranty so if you can get the info your ahead of the game.