Slide-out Floor Rot

Yes windows do leak and allow water to run down the inside of the wall to the floor. Some slides will leak at the bottom of the end areas. Some slides will leak around the seals at the top and sides. Most slide floors are made of OSB/chipboard whatever you want to call it and it does not take much water on this product to start it swelling and rotting. You state that you checked the carpet/rug after every heavy rain, how did you check it ? Did you get down and feel the entire carpet for moisture. It is possible there is a pad under the rug that would limit the moisture from coming up through to the rug. Keep in mind the water has probably ran down the inside of the walls and then out on to the floor. Did the manufacturer not provide an explanation where they felt the water intrusion was from ? I would think they would check for leaks as part of the inspection. It is necessary to find where the water has entered and repair before replacing any flooring else it will happen again.