Thanks. The 5th Wheel is four years old - so no warranty. I agree that the floor in this area is probably not glued down. There is no evidence of water intrusion - no staining, and the stair carpet next to the bubble is dry. I don't know how to rule out water intrusion without damaging the floor. The roof seals are good. As are all other visible seals. I will try the towel and iron fix. Thanks again.
Me, DW & our Choc Lab, Ghirardelli
2013 Chevy Silverado 3500HD LTZ 4WD CC Dually 6.6L Diesel Allison Trans
2017 Jayco Pinnacle 36KPTS