[rverdlm]

First off, since this unit is almost 5 years old and the leak is new I don't see this as a design problem. I also doubt that the area of the seal has changed. I think you need to look for the source of the leak being some where else. Water travels many times long distances in the roof cavity before it finds the place to come in and make the floor wet. I would look for areas that need caulking such as around the windows or up on the roof edges.