Pimples or bumps behind wallpaper
We noticed these hard pimples underneath a window. Did some research and many said it was from water infiltrating and causing the glue to crystallize. We pulled the window and didn't see much evidence...
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I have also found them inside my travel trailer on a wall that doesn't even have a window. There's not a lot of them and absolutely no indication of water damage anywhere. As noted, they are hard, sharp little bumps, not bubbles.
