The scheduler is Started on 20.09 at 16:00 (Period turnaround time), and all tasks including XXXXX.WORKFLOW is also activated, but with "earliest Start Time" "+1 day, Time 19:00". This means that the XXXXX.WORKFLOW should start to run on 21.09 at 19:00.
The task stays active but does not start.
Now on 21.09 at 16h a turnaround happens on the new scheduler. The Scheduler with the old runid gets deactivated, and during this, the current (at the time) status (Active) is also copied in the AJPP table - 1550.
Now, on 21.09 at 19h the job finally runs, but it can not update the value of the Scheduler that started it because the scheduler is already finished - that is why the Schedule Monitor shows the task as still active.
This is working correctly, as it not possible to change values of already finished/inactive objects.