[ovirt-users] botched 3.6 -> 4.0/1/2 upgrade, how to recover

Hello, an old 3.6 self-hosted one-system installation was half upgraded to 4.0 and I took on the task to continue upgrading it. I managed to setup a new engine and upgraded step by step until 4.2 where the host needs to be upgraded. During that time the host was "non-responsive", but I though that this had to do with the upgrade process. Upon trying to upgrade the host the setup broke to pieces. I tried to downgrade everything and restart the old engine to no avail. I now try the way forward to try to start the new engine or create a complete new one, I don;t care much about the old engine's inherited information - all I need to to resurrect the VMs again. At the end of the day the setup is supposed to migrate to a three system hyperconverged setup anyway. How should I proceed to get a working state that fires up the VMs? Is it safe to install a hosted engine from scratch and reattach the domain? Probably the VM configuration will be lost and I will have to puzzle together the disks. I still have the 3.6 engine's backup file, if that is of any help. Should I perhaps recreate a 4.0 engine with that file and try to continue from there? I guess all information on which VMs are attached to which images etc are in the DB of the engine, so I either have to get this info off the 3.6 backup or wire them up again by inspection. BTW this is not a pure ovirt, but an RHV with self-evaluation support, but I believe that any pure ovirt solution will apply. Many thanks in advance.