We have a 2014 Keystone Outback and started noticing a soft area in front of our fridge about 2 years ago. The Fridge and stove are on a slide. We have 1/4" luan on both sides of foam. Lightweight. My assumption is weight of the fried caused the area to become soft. We now have a soft area near a heat duct in front of the kitchen island. We throw a throw rug on the area in front of the fridge now so we can't really feel the softness of the floor. The other area we just try to walk on the slide carpet in front of the area.
We don't have water damage. The floor joists are just too far apart and you can almost feel where it has separated off a joist and is breaking down. We will just live with it and get as much use out of the TT as we can and trade it in down the road. Not worth the expense of trying to repair it as I don't have the skills to do it myself and not worth paying someone to attempt a repair.