Windshield gasket issues

[72cs20]

I had my new windshield installed 3 or 4 months ago with the installer providing the gasket. Now I just noticed that the gasket is pulling away and/or shrinking leaving gaps in areas around the glass.

I went through this very same problem with my former 62 C20 and never did resolve it before it sold.

Is this an installation issue, poor quality gasket...? Anyone else having these problems with their windshield gaskets?

The pics are of the upper passenger side corner. The lower passenger side is doing it too. There were some straight sections that I was able to push back into place. But no luck with the corners.