Unregister/remove files from "VSS repository"

Hi,

Is there a way to unregister/remove a file from the "VSS repository". TSM is unable to backup a file that is not available (remote location, TSM is running as Local System), which shows up as a warning in the backup report.
I know of diskshadow, used that utility to show the list of files that will be backed up as a part of VSS. But that utility doesn't seem to provide any way to unregister/remove files. Need to remove the faulting file from that list.
How do files end up on that list anyway?

Thanks in advance!
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