Backup data from TrueCrypt USB drives to tape?

Hello

I would like to backup data from a TrueCrypt encrypted USB drive to Tape using DPM.  I have mounted the volume and added PG.  However backup to tape fails with errors shown below.

I'm guessing it's a VSS issue with TrueCrypt but wanted to ask if it was technically possible?

Thanks

The back up to tape job failed for the following reason: (ID: 3311) Failure
occurred while adding one or more of the volumes involved in backup operation to
snapshot set. Please check the event log on <server> to
troubleshoot the issue. (ID: 30290)

Log Name:      Application
Source:        VSS
Date:          6/16/2016 12:33:08 PM
Event ID:      12293
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:     
Description:
Volume Shadow Copy Service error: Error calling a routine on a Shadow Copy Provider {b5946137-7b9f-4925-af80-51abd60b20d5}. Routine details IVssSnapshotProvider::IsVolumeSupported() failed with 0x8000ffff [hr = 0x8000ffff, Catastrophic failure
].

Operation:
   Check If Volume Is Supported by Provider
   Add a Volume to a Shadow Copy Set

Context:
   Execution Context: Coordinator
   Provider ID: {b5946137-7b9f-4925-af80-51abd60b20d5}
   Volume Name: \\?\Volume{b29301f1-3052-11e6-80c3-1402ec36e687}\
   Execution Context: Coordinator
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="VSS" />
    <EventID Qualifiers="0">12293</EventID>
    <Level>2</Level>
    <Task>0</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2016-06-16T16:33:08.000000000Z" />
    <EventRecordID>9872</EventRecordID>
    <Channel>Application</Channel>
    <Computer></Computer>
    <Security />
  </System>
  <EventData>
    <Data>{b5946137-7b9f-4925-af80-51abd60b20d5}</Data>
    <Data>IVssSnapshotProvider::IsVolumeSupported() failed with 0x8000ffff</Data>
    <Data>0x8000ffff, Catastrophic failure
</Data>
    <Data>

Operation:
   Check If Volume Is Supported by Provider
   Add a Volume to a Shadow Copy Set

Context:
   Execution Context: Coordinator
   Provider ID: {b5946137-7b9f-4925-af80-51abd60b20d5}
   Volume Name: \\?\Volume{b29301f1-3052-11e6-80c3-1402ec36e687}\
   Execution Context: Coordinator</Data>
    <Binary>2D20436F64653A20434F52434F4F524330303030313739302D2043616C6C3A20434F52434F4F524330303030313731302D205049443A202030303030373334342D205449443A202030303031313234342D20434D443A2020433A5C57696E646F77735C73797374656D33325C76737376632E6578652020202D20557365723A204E616D653A204E5420415554484F524954595C53595354454D2C205349443A532D312D352D313820</Binary>
  </EventData>
</Event>