Hyper-v 2012 VM backup fail when second VHD attached

Hi All,

I have an issue with a Server 2012 VM running on a Server 2012 std host.

The VM is a file server and has an additional VHD attached which contains the files to be shared.  This 'files' VHD is located on a SMB share and attached via disk management.

This works fine for the Guest and allows portability of the actual storage with out being tied to the guest but the back up of the guest VM fails.

I am using windows server back up and only trying to back up the guest VM not including the 'files' VHD (this is done as a file level back up of the VHD) I select the host under the hyper V tree option.

Other guests VMs back up correctly.

I get an error which can be tracked back to this error in the hyperv vmms log:-