triple faults on windows guests with bhyve 13.0-RELEASE

Hi all

I've been having ongoing issues with windows ( 10, 11 and 2019 ) just 
spontaneously halting with  an status 3 exit (triple fault). Guests will 
run for weeks or days or less than an hour.

I have set these up using vm-bhyve and am using virtio-net for network 
and nvme for disk ( storage is a file ).

The host is running on 13.0-RELEASE-p11 on a Threadripper 1920 12-Core 
with 128Gb memory with zfs.

The machine is part used as a home lab with 4 windows vms, a couple of 
pfsense vms, a linux vm and about 10 jails.

I thought perhaps it could be the version of virtio-net (I have tried 
several versions and 185 seemed more stable, but last night win11 and a 
win10 both stopped (at different times). After a restart the win10 vm 
halted 5 minutes later.

What I would appreciate, is some indication of where to start, to create 
some type of crash dumps etc. to help figure out what is causing this.

regards

Duncan