Up until this point I’ve kind of just been shooting spray foam into the gaps of my windows, assuming that everything was properly installed. Quickly discovered that there was no proper sealing when I saw foam running past the exterior trim.

I honest to God have no idea how these are mounted because I don’t see any shims in the gaps do I see a newer style flange sitting on the osb. In this video, I’m pressing against the trim from the inside and there’s no flange and the OSB stops further down midway through this horizontal 2 x 4 in the frame.

In any case, nothing seems to be properly sealed or flashed hence why I’m seeing a lot of my exterior OSB rotted out near the windows. Is my only recourse to add OSB and extra framing and then reinstall the Windows after proper flashing?

https://imgur.com/a/pg1Z1Jn