@Danp Thanks for looking into this...
Restart: Yes, Pool Master was restarted after applying the XCP patches
VM start: Yes, I'm trying to start the VMs on the master (also, it would not allow me to start VMs on the slaves with XenServer on it during the migration phase)
Upgrade Path: Yes, vrom XS 7.1.2 to XCP 8.3
Regarding the VM_HOST_INCOMPATIBLE_VERSION: I saw those, too, but cannot think of anything obvious, as the VMs which I was able to start on the Master were of the same kind (WinSrv2019, Ubuntu Server, Win10). Of course, there might be slight differences in the metadata, but I've compared two WinSrv2019 and they are pretty close. Only "RW/MRW" differences found:
HVM-boot-params (MRW): order: dc; firmware: bios
HVM-boot-params (MRW): order: dc
platform (MRW): ...; secureboot: false
platform (MRW): ...
I've removed those two param keys from the failing VM but it did not change the behaviour.
