Unable to unmount

Hi

I'm unable to unmount a Datastore from an ESXi host.

The Datastore successfully unmounted from 2 ESXi hosts but not the third one.

There are no VMs on the Datastore, Storage I/O is disabled, it's not in a Datastore Cluster and it's not being used for HA.

There is no content left on the Datastore except one folder called .sdd.sf which cannot be deleted.

The error when attempting to unmount the DataStore is:

Thanks in advance for any help.

Regards

Eoin