Unexpected reboot of TrueNAS

I’m troubleshooting a random reboot from earlier today, where TrueNAS went offline for 25-30mins before coming back up.

In the logs, it seems like something called for it to shutdown

Nov  4 12:36:20 NAS-Tank systemd-logind[4050]: Power key pressed short.
Nov  4 12:36:20 NAS-Tank systemd-logind[4050]: Powering off...
Nov  4 12:36:25 NAS-Tank systemd-logind[4050]: Delay lock is active (UID 0/root, PID 4738/libvirtd) but inhibitor timeout is reached.
Nov  4 12:36:25 NAS-Tank systemd-logind[4050]: System is powering down.

but the server is securely located and I was the only one in the building so I know it wasn’t pushed. Could a faulty motherboard pin/header trip it?

Or could the BIOS trigger this sort of shutdown? All temperatures of CPU and HDDs were <40C and relatively idle.

I did spot from monitoring that ZFS ARC was using 110GB of the 128GB RAM in the system, with 1 VM running using 8GB, but I’d expect logs for OOM if that was related.

Any ideas?