Windows Server Essential 2019 problem
Often problems require deep analysis, from the installed application to the entire customer environment. And so it was in this case.
The virtualized Windows Server Essential 2019 system was rebooting every specified period of time.
Deep log analysis (yes in Windows this is possible too).
The cause was found.
We “promoted” the system to a Windows Server Standard 2019 environment without reinstalling the system.
Another customer satisfied.