Windshield continuously pops out.

I bought a used 2000 Fleetwood Bounder 39Z. the previous owner and friend of mine noticed the gasket had come loose on the passenger side top corner. So he had a glass guy reset the glass, so it wasn't leaking. I had it out driving it around and having some minor work done and it was leaking air again. so, I took it to a guy who got it pushed back into place again. it has now come out for a third time and I'm hearing from some other glass companies this is a common issue, but no one seems to know how to fix it or what needs corrected so it doesn't continue to happen.

Has anyone had this issue and know of a solution?