What would cause this and what would it take to fix it?

[family affair]

My guess is screws are over torqued. Would the windshield need to come off to fix this?
Ballpark cost?

 

[SkunkBoat]

Yes screws in windshield....not tapered when drilled..crack widening....water freezing....
To do it right yes windshield off or loose....or just fix what you see.

cheap DIY

Marine-Tex $12 and an old fashioned can opener to scrape the line into a v groove