Being trying to fix this for a few week now, and i seem to be going around in circles. The monitoring tool we use keep showing the following
4 x VSS ( EventID=8194 )
Volume Shadow Copy Service error: Unexpected error querying for the IVssWriterCallback interface.
2 x VSS ( EventID=7001 )
VssAdmin: Unable to create a shadow copy: Either the specified volume was not found