Everything that could have gone wrong with the Chicom shell, did. I had to fab a mounting system because the harware they sent was for God knows what. That being said, it's mounted. It looks pretty dang good and will make life so much easier.
1/2" or 5/8" drywall? Should be 5/8" for truss spacing. I would have guessed moisture. Truss uplift usually cracks drywall, but maybe it worked on the nails over the years.