[rverdlm]

Sharon, I had a couple of spots like that in my last trailer. That trailer never leaked (we lived in it so we would know). I have no idea what caused it, they never broke through, and they caused no other problems. My thought was that the product behind the surface we see is glued together in some way and the glue in a certain area is weeping out. Since yours sits in storage much of the time it probably gets very hot inside at times and this would make the situation worse.