Symptoms
In the summary section of the agentless backup job log there were Extended error message like:
xx.xx.xx.xx sssvh Thu Oct 28 04:34:10 2021 SNBSVH_826E ............Extended error: There has been some problem in processing disk ([GOZER_dpxqa65_lun0] 62.131 OEL 7.4 (Wendy)/62.131 OEL 7.4 (Wendy)-000001.vmdk), reason ( disk ([GOZER_dpxqa65_lun0] 62.131 OEL 7.4 (Wendy)/62.131 OEL 7.4 (Wendy)-000001.vmdk) is an independent disk and is not supported)
xx.xx.xx.xx sssvh Thu Oct 28 04:34:10 2021 SNBSVH_826E ............Extended error: There has been some problem in processing disk ([GOZER_dpxqa65_lun0] 62.131 OEL 7.4 (Wendy)/62.131 OEL 7.4 (Wendy)_1-000001.vmdk), reason ( disk ([GOZER_dpxqa65_lun0] 62.131 OEL 7.4 (Wendy)/62.131 OEL 7.4 (Wendy)_1-000001.vmdk) is an independent disk and is not supported)
Resolution
In looking at the virtual machine itself, there is no independent disks are configured, VM was in the state suggesting that Consolidation was needed. An attempt at Consolidation failed because of a lock. This is often an indication of a hotadd disk of a prior backup not being removed at the end of the backup. Looking at the all the agentless proxies that could use hotadd with the affected VM, two still had snapshots of VMDK attached from the affected system. These were detached using VCenter "Remove from Inventory". With the disks detached, the Consolidate completed. and the next instance of the backup completed successfully.