I did have a problem with my audio when first turning on the TV. STB is always on. If I changed the channel or the volume, the audio was back. Not much of a problem, but it started this a few weeks ago. I think it was when I was getting the green screen. Checking here in the forums the solution was a hard reset. I did that, but the wife was holding the remote and she must have hit some buttons by mistake. I did catch a glimpse of what you call the STB Menu. I believe that was when the audio problem started.
I searched here to find out if anyone else was having that problem. I didn't find exactly my situation, though there were other audio problems. Going through those pointed me in the right direction.
Using the STB Menu, selecting the audio setting, then changing PCM to Auto, seems to have fixed it. Now, when I turn on the TV the audio is there.
Thanks to all those that post help here and I hope this post helps someone else.