Start looking at things above the window. Our driver's side window had a leak in hard rain. We had the window out for repair at RV Fog Dr. and they sealed it well. It still leaked.
I had the folks at CC take the window out again to treat some rust on the metal frame (RV Fog Dr. did a great job de-fogging the glass but lousy job of treating frame rust). The tech at CC found a tear/opening in some caulk along the roof-to-sidewall area. He fixed that and another suspicious area around the driver's side horn. Window hasn't leaked since.
'07 Country Coach Allure 470 Siskiyou Summit #31578, Cummins ISL 425; 2014 Ford F150 toad; Air Force One Toad Brake.
Glen Allen, VA; Smith Mountain Lake, VA.