System: Windows Server 2016 Standard, fully patched, both host and guest(s).
A strange thing happened today when I rebooted one of my Hyper-V guests (by RDP-ing to the guest and manually triggering a reboot). Here are the relevant parts of the event log:
11:38:32 The operating system is shutting down at system time 2020-07-09T09:38:32.812302400Z. 11:41:00 The operating system started at system time 2020-07-09T09:40:59.495420000Z.
11:40:39 The operating system started at system time 2020-07-09T09:40:38.490643100Z. 11:40:39 The last shutdown's success status was false. The last boot's success status was true. 11:40:51 The previous system shutdown at 11:38:05 on 09.07.2020 was unexpected. 11:40:42 The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly. (BugcheckCode 0, BugcheckParameter1 0x0, ...)
It appears that the guest successfully rebooted, and, in the short instance of time that the guest was shut down, the host decided to power cycle, which looks ... strange. The host and the guest's clocks are perfectly synchronized.
Is this a known issue or an indication of some hardware fault? If the latter, educated guesses as to the cause (SSD, RAM or system board) are welcome.
Some additional background (don't know if it's relevant, I'll include it just in case): The host does BSOD every few months(!) with Bugcheck Codes that point to faulty hardware (although I haven't been able to determine the culprit by examining the minidumps yet, there are no device drivers in the stack trace or other obvious clues). The last time (two months ago) I switched the order of the RAM chips, and there has been no BSOD since. Since those BSODs occur so rarely, they are almost impossible to debug with the usual technique (I can't, for example, run the host with half the RAM for half a year just to see if that fixes the issue). Memtest86 reported no errors, but I know that this does not necessarily mean the RAM is perfectly OK. It's a HP Microserver Gen10 with ECC RAM.