It's been happening between 6:00 AM and 6:59 AM. I have Windows Update set to download, but ask to install. I just updated all the patches today, so I'll see if it resolves the problem. The system was restarted this morning after the crash and was idle 9:00 AM to 6:00 PM, so 9 hours. That's less time than the overnight crash. We'll see how it handles idle overnight after heavy recording this evening.
FWIW, this is one of two identical machines. There is a third that is nearly identical, but uses the 2011 Mac Mini Server for its build. None of these machines are experiencing the same behavior. Makes it all the more frustrating.