Symptoms:
This issue is caused due to incorrect/stale resourcepool reference in the provider VDC table.
Using the above log snippet as an example, the moref expected is resgroup-67890 but the value present will correspond to the resourcepool which was removed/decommissioned (example: resgroup-12121) and is returning the nullpointer exception when the migration is carried out.
To resolve this issue, please open a Support Request.
Database modifications are required to update the Provider VDC entries and require VMware Technical Support assistance.
Warning: A backup of the Cloud Director database must be taken before attempting to make any changes to it directly. For appliance-based setup, follow https://docs.vmware.com/en/VMware-Cloud-Director/10.3/VMware-Cloud-Director-Install-Configure-Upgrade-Guide/GUID-9562FBC9-4537-4FE6-B1CC-005C232A556D.html.