Just noticed the same thing on the front bunk on my 21SS. Just sort of a slightly warped looking area in the lower left corner. I checked the bunk end when we let it down but couldn't find any evidence of moisture on the wood or canvas in that area. I didn't have a camera handy to take a picture. Is there something else I should be checking?
Ann ("Older than springtime, younger than dirt.")
Molly, my rescued cockapoo, who loves camping
2013 Rockwood Roo 21SS
2003 Dodge Durango SXT w/full towing package