Don’t know if it would help, but I have a peculiar setup to be able to monitor 2 /24 networks (1 BgE and the other wifi, all bridged into the HA VM).
Story here:
The HA VM only got stable after I defined a default gateway for the second "virtual’ nic. Of course, I configured an IP outside the same network so it is unreachable.
If I left the second nic without a default gateway, it would reset to automatic, although I had chosen for it to be manual.
In fact, will try to upgrade again but removing the second nic first.