I'm having this same issue (3 times) with my 2014 Sierra and have had it addressed trice at the dealership. They claimed both times that the issue was corrected by re-flashing the IntelliLink system. I actually had it recur about a week after the second fix. I have a video showing the issue which I will try to post. I have attempted to read through as many posts as I could find and have not found that anyone has found a solution. If there is one, would you please let me know?
Ultimately, I am attempting to have someone with GM customer service reply to this. I have contacted them and the reply I received was generic and doesn't seem to be going anywhere.