To resolve the issue, the transfer directory needs to be mounted correctly on the Cloud Director Cell(s).
The issue occurs at the final stage of the log collection, so the log bundle will be generated but not copied to the transfer area. The log bundle can therefore be manually copied off the Cloud Director Cell(s).
It should be found in the directory from which the /opt/vmware/vcloud-director/bin/vmware-vcd-support command was run.
For more details on the transfer directory requirements see the VMware Cloud Director documentation here:
Preparing the Transfer Server Storage for the VMware Cloud Director Appliance
Preparing the Transfer Server Storage for VMware Cloud Director on Linux