I was checking the silicone sealing around my RPOD and found a corner had water infiltration. When pushing my fingers up under the the corner (underCarriage) it was found to be soft. I used an oscillating saw to open it up from underneath and found the cheapest thin plywood rotting out. I have traced and tied the actual damage to the way the water runs off the back of the trailer. The manufacturer did not install a drip edge so as to stop the water from curling up under the undercarriage and getting through the plastic barrier and into the floor. I have since installed a drip edge along the back of the trailer and siliconed it so water drops off lower that the flooring. I used aluminum carpet transition as a flashing.

I also used corrugated plastic with construction glue to replace and rotted undercarriage and then used Gorilla waterproof tape to seal it all in. thought I would pass the tip along to other members to add a drip edge to avoid this problem of water running down the back of the trailer then curling in under and wetting things out.