Winnebago windshields are glued in place. You may have rust behind the windshield pushing it out and allowing water in. That is a common issue with Winnebago and has occurred with both of my split windshields.
The expansion caused by the rust caused both windshields to crack and the drivers side leaked water that ran down the inside. I did a temporary fix with butyl windshield tape pushed into the track above the windshield.
I have had them both replaced at the Winnebago factory,the rust removed and the area treated. I also asked them to seal the area above the windshield.Cost was about $1200 each. Insurance paid all except the deductible.