Hypervisor is running the latest version of 7, and was working on upgrading to 8. I shut down all of the VMs to prepare for the upgrade. In doing so, the Proxmox host itself stops responding through the web interface, stops responding via SSH, doesn't reply to pings, and the console itself stopped responding to keystrokes - it locks completely up.
This host only runs 1 container, 1 Windows VM, and an occasional GNS3 simulation VM that stays powered off most times. As soon as I shut...