Lost Sound

My sound randomly goes out. Perfect picture and the box responds to the remote for all features. No issues with the TV sound. It works fine if I switch to a different input. The only thing that fixes it is to unplug the cable box. I then have to wait almost 7-8 minutes for the box to restart. I've run the box  update mutilple times and it doesn't fix the issue. It happens when I start watching DVR'd shows and when watching cable. Never predictable.