KVM with Windows 10 x64 guest crashes to terminal intermittently

New forum user here, so please forgive any noobiness…

I have recently installed openSUSE Leap 15.4 KDE on a Dell Precision 5530 using an ACASIS external NVME USB-C enclosure as the primary disk using secure-boot and a UEFI partition. After some tweaking this appears to work as expected (fast even)

I installed KVM then created a Windows 10 x64 virtual machine, installed the OS vanilla, and installed the virtio drivers. I’ve noticed that after some time the laptop fan spins up and eventually Plasma becomes unresponsive and drops to terminal regardless of the cpu/memory/disk/network activity. From there any attempt to reboot the system ends up with a shutdown failure and a hard power-off is required. I have noticed that after this the UEFI boot option is missing unless I remove/reconnect the external drive and power first… not sure if this matters.

I tried changing the CPU/Memory/Disk settings, I have enabled/disabled OpenGL, and have tracked the time to failure to pin down any pattern with no success. The only repeatable symptom so far is that the fan spins up before the crash; having said that neither the laptop or the external drive are hot to the touch and the battery is fully charged/plugged in. With no VMs running, the fan is quiet and Plasma runs as expected.

Has anyone experienced anything similar or have a reasonable hypothesis for the kind of behavior I am seeing?

Thanks in advance!