Had a Winnebago Sightseer and the windshield leaked. Dealer pulled out 2-piece windshield and put sealant in and reinstalled it. Still leaked. Took it back, they redid it with a different sealant. Scrapped out previous sealant,
put different sealant in and reset windshield. Ended problems.
Had a 2009 Hurricane and water running down inside. Came from all the ICC lights. Removed, sealed the ICC lights and no more water.
x2 on seals shrinking due to hot, dry weather... same applies to seals around the windows.