Scheduled task not running on 20 minute interval and only running every 50 minutes on 21 minute interval

Question

When using the following schedule setting our "Synchronize vacancies from ATS" scheduled task is never started.

20190922|99990101|127|00:20:00

The logs show the following message every ten minutes

Not due: Synchronize vacancies from ATS

When I changed it to

20190922|99990101|127|00:21:00

The logs still show the following check each 10 minutes, with an exception of each 50 minutes where we get a successful start.

Starting: Synchronize vacancies from ATS (asynchronously)

Answer 1

The solution to this problem was disabling the following file on the prc instance App_Config\Sitecore\CMS.Core\Sitecore.Processing.config.

You need this file only if you specifically want to run scheduled items on your processing instance. By default there are none. So if you have not created any of those yourself there will be no impact.