Intermittent pump operation
When my 8280ws was in for service, I had the dealer check out the water pump for a cycling issue every 15 minutes or so. I had thought the check valve was back flowing in the pump. This was to be covered by the FR extended warranty. What was found was a leak in the worst place possible, under the floor by the stairs. They had to remove the steps and furnace to replace 20 ft of water lines going to the low point drain. I never saw a single drop of water indicating a leak underneath the trailer. I'm guessing the amount was less than what would accumulate and run off the bottom cover. The dealer said that FR typically would not cover the leak under extended warranty. They did convince them to cover the cost by showing them is was a problem with the build.
This is another example of how choosing the right dealer is so important when buying.