Duplicate Shedule idetifier dissappears once a manual run of the job takes place
Setup is as follows:
Backup to disk and Duplicate to tape one the source has completed.
If the Duplicate element is run manually (eg in the event of a failure to tape for whatever reason) then the Schedule identifier that shows you have selected to duplicate once the source job is complete dissappears.
Bizzarrely once the backup to disk runs again according to schedule the duplicate will still run as originally configured.
The issue here is misleading the administrator that a setting is unset when it actually is set!