Why engine-backup restore is failing with error "Failed restoring /etc/ovirt-engine"?

Issue

• The original RHV manager was accidentally upgraded to RHEL 8.9. Then a backup was taken from 8.9 and is now being restored to another RHEL 8.6 server.
• This engine-backup --mode=restore is failing with the error below:

2024-01-21 20:31:11 28472: Restoring files
tar: var/lib/grafana/plugins/performancecopilot-pcp-app: Cannot open: File exists     <===
tar: Exiting with failure status due to previous errors
2024-01-21 20:31:11 28472: FATAL: Failed restoring /etc/ovirt-engine        <===
/var/lib/grafana/plugins
/var/lib/grafana/png