Backups fail with The requested object was a duplicate (4045691)

Backups fail with The requested object was a duplicate. For example:

Replay.Agent.Contracts.Transfer.TransferFailedException: The transfer failed: 'There was a problem with the VSS subsystem on 'AgentX'.' ---> System.AggregateException: One or more errors occurred. ---> Replay.Core.Contracts.Transfer.VssGeneralErrorException: There was a problem with the VSS subsystem on 'AgentX'. ---> Replay.Agent.Contracts.ShadowCopy.ShadowCopyException: Error snapping volumes (C:\;(Volume Labeled 'System Reserved');C:\;D:): The requested object was a duplicate. ---> Replay.Common.Contracts.ReplayException: The requested object was a duplicate.

In this instance, the failures were due to volume C: bring in two separate protection schedules at the same time. This should not be possible:

1. C: was in a schedule by itself at 11:16 PM.
2. C: was also in a schedule with (Volume Labeled 'System Reserved') & D: at 11:17 PM.

To verify, go to the Summary page of the agent and look at the Volumes section to see protection schedules.

Solution:

NOTE: This will trigger a base image fore the volume having an issue.

1. Remove the volume from all protection schedules:
   1. Click Set a Schedule and remove the volume from the first protection schedule, click Apply to save your changes.
   2. Repeat for the 2nd protection schedule.
2. Optional, but suggested, click Refresh Metadata so updates are pushed to the agent.
3. Select all volumes, click Set a Schedule, add volume back to the default schedule, and click Apply to save your changes.
4. Force a snapshot, backups should be successful.