Recently upgraded to CDOT 9.1.
VSC 6.2.1 (Vsphere/ESXi 5.5u3).
Attempts to restore any VSC VM backup errors out on the "resignature unresolved VMFS volume" step, with an error status:
"A VMFS volume with the same UUID [###] is already mounted in the datacenter."
Never had this problem with 7-mode.