Well, I think this is a new one.
While prepping for an upcoming 8,600 mile trip with the family, I discovered an approximately 6"x6" raised bubbled area on my EPDM roof, right next to the low corner of the shower skylight, right above the showerhead inside the coach. It is spongy in both feel and appearance.
Assuming there was a sealant leak, I did a careful visual inspection of the area, including a search for small cracks in the skylight itself and pinholes in the roof. Nothing was found. In a epiphany, I went below and removed the inside assembly of the skylight, exposing both the framing members and the outside layer of skylight. Aha! Although there was originally a 'vapor barrier' installed (actually, just some mastic tape) it had dropped loose. Since I have used the RV for the last two years to live in while away from home due to work, I am assuming that the hot mist from my daily showers managed to migrate around the inside layer of the skylight and accumulated in the underside of the EPDM. Since the RV has been in use through the last two winters, I'm sure that delamination due to freezing temperatures has caused the bubble.
Now I'm stuck. I've got a moist spot under there that needs to be addressed. I need to cut out the affected portion of the roof, repair the damage and then reseal the hole. I am assuming once I have finished repairs (including the vapor barrier), I can either slap a piece of Eternabond over the hole and cover it with some Liquid Roof or use an EPDM repair kit and just fuse an EPDM patch over the hole. Is one method preferable over the other, or is there another better method?