Manager job schedules and re-starts Queue-able jobs for the Scheduler (which in turn processes AGs and assigns records). These are normal Salesforce scheduled jobs (synchronous) and run every 30 seconds (each one schedules the next one).
Occasionally, we have observed the Manager job getting stuck in the backend due to a Salesforce issue/bug, especially when they are performing upgrades within the instances. The frequency of Manager jobs getting stuck may vary from org to org.
To check if the Manager job is stuck, go to QA Control Panel > Process Monitor.
First, check if the Manager job is being scheduled or not by clicking 'Refresh'. If the 'Next Run Time' for Manager is not showing as the current time and not updating after refreshing multiple times over a couple of minutes, then the Manager job is stuck. In that case, simply have an Administrator click on 'Restart Manager' to restart the job.
Once done, continue monitoring Manager for the next 5-10 mins to make sure Q-assign is working as expected.
Please contact us at firstname.lastname@example.org for any questions.