@jb
You have hit on something that ties into what I have discovered. Since July 1, on my XCP-ng / XO-CE cluster, the metadata and xo-config backup job only runs successfully when I have all 3 hosts in my cluster active, and after I have reset the tool stack on the Master host.
Because I am running the XCP-ng and XO-CE on an off-grid solar/battery system, independent of my electric bill, I try to limit total power to 250 watts for all devices (network switches, iSCSI NAS, XCP-ng hosts, etc). Consequently, I run only one host on a regular basis. When it is necessary to update XCP-ng, I turn on all hosts and do a rolling pool update. If I manually perform a metadata and xo-config backup while all of the hosts are on, only then will the backup be successful.
Before July 1, the metadata and xo-config back was always successful, whether it was scheduled or manual.
Hopefully, this will turn on a light bulb in the head of a Vates engineer, and he or she will solve this issue!