VSS is Micrsoft's snapshot service. It is very powerful, but has many failure modes making it hard to diagnose the cause of errors.
Any VSS error will cause the backup to fail with Backup aborted! - Failed to create volume snapshot error.
Note that on some 32 bit systems, Reflect will fall back to the paramount snapshot component pssnap. This will be noted in the log, the snapshot and backup will still be valid.
Getting detailed error information
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