Well I don't want to say it's impossible but I have looked in the wall and don't see any moisture in there. The windows never fog up in there. Sometimes they do in the bed area when my windows are closed but never the bathroom. I've never experienced a true winter while living in here so I don't struggle with condensation issues like a lot of fulltimers do, as I am heat seeking and go south in the winters.
Yes! The flooring does go under the sink and it is quite thick. I was almost sure that was the issue but now that I am seeing a similar issue beginning to develop on the wall where the dinette booth meets the "exterior" wall, I'm wondering if it's a bigger problem. Better picture below of where this is happening.
