KVM virtual machine shutdown hangs host!?!?

I have a Pop!_OS desktop, on which I run a KVM virtual machine using Virtual Machine Manager for Windows-only stuff (like my work softphone). This has worked fine for a long time, but recently that changed. When I shut down the Windows 10 VM the desktop host hangs. Clearly that is never expected or wanted! I have to hard reset the host motherboard to get Linux to restart.

I have checked for any pending updates to Pop!_OS and there are none. As of today - I have Pop!_OS 22.04 LTS, with kernel 6.06.-76060006-generic.

I need ideas on how to start the diagnosis - where should I look for pertinent log files?

This seems to have gone away, so I assume some of the recent updates have resolved it.