If the water comes in the cupboard above the couch that rules out slide seal problem. Since the leak is obviously at the outside flange to the roof mount it should be easy for the Dealer to open the slide and just run a water hose direct on the roof for a few hours. This type problem really needs a air pressure test which will show where the water is getting in. The reason it leaks more when closed is because the outside slide metal flanges torque and if not sealed correctly "open" up a small gap for the water to go in. Doug
