If you are running ESX or ESXi U2 or above and have an application that creates VMware backups using snapshots (e.g Vizioncore , Veeam ) you may notice sometimes you are left with a snapshot called Consolidated Helper Snapshot followed by a number.

If you try to remove the snapshot on a powered on VM it will fail (hangs at 95% ) and you may find that when you right click the virtual machine in VI client you can no longer power off the virtual machine and most of the other settings are greyed out.

Saw this happen to a VM running on an ESXi host after aborting a backup script, only thing I could do was reboot the ESXi host and remove the snapshot whilst the VM was powered off, all OK then.

These helper snapshots from what I can determine are designed to reduce the impact of VM snapshots locking a live VM but may occasionally not get removed correctly after the removal of the main VM snapshot.