In cold climates some of those leaks may not be from the outside. The domes are very hard to get "attic ventilation" because "Where is the attic?". In climates were the vapor retarder is on the inside it takes an good installer who is very patient to get a good seal. And if the installer is not carefull there is no where for the moisture to go, so it rains back through the hole it seaped out of in the first place. The few I have seen here in Alaska are showing signs of moisture damage but I have inspected a couple where someone used ice and water shield on all the seams and urethane or foam insulation.