The backup gets to about 87% before failing.
Usually at this stage, it is getting stuck at the remval of snapshot process
Please check the failing VM, go to virtual center or vSphere client, take a snapshot of this VM, see if it creates it successfully, then go back to snapshot manager and do Delete All. This should consolidate all the open snapshots, if it is stuck and 95% and cannot remove snapshot, then it could be an issue with VM itself, try rebooting the vm first, if still an issue then Un-register and then register the VM. If still same issue with removal of snapshot, please follow this VMware KBs or contact VMware support.
http://ict-freak.nl/2009/07/11/vmware-remove-snapshot-stuck-at-95/
