How to debug LIVE migration ?

[lejeczek]

Hi guys.

I am experiencing a peculiar situation where LIVE migration 
between boxes:

A&B have Ryzen 5 3600
C has Ryzen 5 5600G

I highlight CPU bits as rest of the hardware & OS are virtually identical.

with 'virsh' I can:
1) LIVE migrate a OK:
between A & B
from C to A &| B
2) LIVE migrate says okey, reports no errors but instead VM gets shutdown + 
start
from C to A - fails!
from C to B - fails!

To make it even more peculiar - if possible that is - I've fiddled with CPU models 
such as qemu64 & kvm64 but it all fails, where fails, the same.
How to debug this going to Qemu's level?
As for Libvirt' and OS' logs - there is not much if anything at all saying, 
suggesting there is a problem, no segfaults, no crashes.

All suggestions & thoughts greatly appreciated.
many thanks, L.