Seeking advice or comment on similar problem. Recently purchased our 2015 Elkridge 35TSLR thru a private sale opportunity. While cleaning the walls around the pull out sofa (on back wall) I found the wall area from the window down to floor to be soft and spongy. Obviously water damage and the sound of dry rot wood behind the panel. Completely undetected just looking at it until you put a hand to the panel and feel it give. My question is would I be able to remove the lower damaged area and replace with new lumber panels from the inside. The outside of the panel seems to be solid and firm. Or is this an issue that requires the entire rear wall panel to be replaced by a service center? Unable to detect the leak but my guess will be the exterior window trim and or the corner seams where the AC water runoff has traveled. Suggestions on taking on this repair ?