There is a forum called inside GM news. I would post your issue there. I posted there when the paint was peeling off of my three year and one month Sierra. The dealer pretty much told me to kick rocks. After I posted there I got emails and calls from GM asking me how they could help. That worked for me. I would recommend trying that.
1969 x-77 Z/28 orange/ white stripes, named by my daughter "Clementine ", M-22 close ratio, 4:10 12 bolt, CE 302. Hugger orange with white stripes. White standard interior. Restoration complete May 2018