ESXi Host configuration backup fails

Recently upgraded to: DELLEMC-ESXi-6.0U3-5224934-A03 and  while trying to create a host configuration backup, I get the following result:

C:\Program Files (x86)\VMware\VMware vSphere CLI\bin>vicfg-cfgbackup.pl --server=10.2.1.201 --username=root -s c:\cfgbackup.tgz

Enter password:

Restore failed: A general system error occurred: Internal error

I have tried with the vCLI 6.0, vCLI 6.5. Why does it say "restore" failed????

Also, when I try to run the backup from the host, I get:

[root@esxi1:~] vim-cmd hostsvc/firmware/sync_config

[root@esxi1:~] vim-cmd hostsvc/firmware/backup_config

(vmodl.fault.SystemError) {

   faultCause = (vmodl.MethodFault) null,

   reason = "Internal error",

   msg = "Received SOAP response fault from [<cs p:1f2b6498, TCP:localhost:80>]: backupConfiguration

A general system error occurred: Internal error"

}

[root@esxi1:~]

Any ideas? THX