ERR - Error encountered while attempting to get additional files for System State:\

Errors seen in log:

unable to find first file: 'Shadow Copy Components:\System Service\Background Intelligent Transfer Service\' 
INF - file System State:\Automated System Recovery\BCD\BCD skipped 
 ERR - Error encountered while attempting to get additional files for System State:\  
 INF - Enabling volume snapshots for (System State:), please wait... 
 INF -   Adding Volume System State:\  
 INF - Unable to snapshot volume (Invalid source volume): System State:\ 

Suggestions:

1. Use Windows backup utility to backup System State to local disk.
   Tell us what the result is.
2. Split your backup into multiple data streams (select 'allow multiple data streams' in policy attributes.
   This way backup of other drive letters on this server will (should?) go through. Please only make this change before full backup is due to prevent Incr backup from running as Full.