Issue when backing up FreeBSD guests

Hi,

I'm currently evaluating VMProtect within our vmware esx5 enviroment.

Backing up windows guests works fine however all the FreeBSD guest machines succeed but with the following warnings.

Detailed message

Failed to execute IO operation 'Open'.
Additional info:
--------------------
Error code: 246
Module: 83
LineInfo: c61573f663f5d800
Fields:
Message: Failed to execute IO operation 'Open'.
--------------------
Error code: 208
Module: 83
LineInfo: c61573f663f5d756
Fields: code : 15
Message: VMware_VDDK: The file is already in use
--------------------

The freebsd guests have the VMware Tools installed.
What does this error mean and how can I get the FreeBSD guests to backup without warnings.

Thanks