On the SSPI UI, when you try to take backup, it fails with the error as shown in the screenshot.
SSP 5.1
This issue may occur when the backup process obtains the cluster snapshot from clusterctl, which looks for all available objects and their relationships and does not find sync between Nodes, vSphere machines and VMs.
And due to the mismatch in the numbers of objects SSPI backup fails.
Contact broadcom support to troubleshoot this issue.