We just bought a new 2018 Tab 320s boondock on Friday. Looking under the back cushion, I notice a darkened stain around the corner area of the right rear. It's not wet, and I see no buckling; but I find it concerning. My first thought was maybe they just used discolored wood there because it's in an area that doesn't show. But then again, the shape of the staining looks almost like water was standing in that corner for a time. Thoughts?