Backups to deduplication go into queued state after an excessive amount of media has expired.
OST media is on a special reclamation cycle that once the media overwrite protection has expired, the media is reclaimed during each backup and duplicate job.
This aggressive type of media handling is in place to address space issues that can occur in a deduplication storage folder.
If a large number of media expire in a short period of time, the media will then que up to be relcaimed at the next run of the backups.
This can make the jobs appear to stall/hang, but in actuallity, the aggressive media reclamation is working to free space in the deduplication storage folder. seemlessly behind the scenes, without user intervention.
If an excessive amount of media is has expired and multiple jobs are running, this stall/hang may seem more prevalent.
If Central Administration Server is deployed and coupled with Wide Area Network links to Managed Media Servers, the operation to reclaim the expired media can range in variety.
Should this operation cause undesirable job completion times or missed backup windows, Tech note TECH159843 contains information to disable the feature temporarily to allow the reclamation to be bypassed and backups to run.
This is a temporary workaround and not to be used for any length of time and is merely to allow needed backups to complete within the time requirements for each customers environment.
This isssue has been resolved with a Hotfix