📄️ Cron events that have missed their schedule
The WP-Cron system in WordPress is not a "real" cron system, which means events may not run exactly according to their schedule because the system relies on regular traffic to the website in order to trigger scheduled events.
📄️ Problems spawning a call to the WP-Cron system
If you're seeing an error message saying there was a problem spawning a call to the WP-Cron system on your site, this indicates a problem that is preventing cron events from running. If you can see cron events that have missed their schedule by more than a few minutes, this is almost certainly a problem you need to investigate.
📄️ Problems adding or editing WP Cron events
Unfortunately the WP-Cron system in WordPress isn't totally reliable when editing, deleting, or adding new events, particularly on a site with many events so that one may be running right around the time you save your event, and on sites with a persistent object cache.
📄️ PHP default timezone is not set to UTC
If you're seeing an error message saying PHP default timezone is not set to UTC it means the timezone that PHP uses on your server has been changed from UTC to another timezone. This is a misconfiguration that you'll need to fix.
📄️ This interval is less than the cron lock timeout
If you're seeing an error message saying This interval is less than the WP_CRON_LOCK_TIMEOUT constant it means the interval at which events with this schedule are due to run is less than the interval at which WordPress core actually runs events.
📄️ WP-Cron is being managed by a plugin
There are a few third party plugins available which connect to systems that take over the running of cron events on your WordPress website. When WP Crontrol detects one of these it shows you a message for informational purposes, but there's no action you need to take other than to be aware of how cron events are processed on your WordPress installation as a result.
📄️ URL and PHP cron events that need to be checked
In WP Crontrol version 1.16.2 (released March 2024) a security hardening feature was added which prevents the code in a PHP cron event from being tampered with. You can read about PHP cron events here.