Error code: could_not_set, Error message: The cron event list could not be saved

[Arlingtoner]

Things are generally going well, but every once in a while, I notice that one of my database tables has stopped being updated. That is because a Cron Event that does the updating has disappeared and I find an error message like the following in the WordPress debug.log:

[12-Nov-2025 19:20:15 UTC] Cron reschedule event error for hook: vhc_SitePowerDaily_hook, Error code: could_not_set, Error message: The cron event list could not be saved., Data: {"schedule":"every-15-minutes","args":[],"interval":900}

If I click on Add New Cron Event and re-add the event, its Cron Events entry looks something like:

vhc_SitePowerDaily_hook                                    in 6 minutes                       Every 15 minutes          vhc_update_site_power_table()
Edit | Run now | Pause this hook | Delete            Today at 2:05 pm

and everything is fine until the next time (days or days and days later).

What is going on? What can I do to prevent the error?

[johnbillion]

The underlying problem is most likely this unresolved bug in WordPress core: https://core.trac.wordpress.org/ticket/57271 . When there is a problem rescheduling a cron event (ie. the option cannot be written to) then WordPress triggers this error but doesn't attempt to recover. If the cron event is one that you added through WP Crontrol then it can cause it to disappear.

I'm not currently focused on solving this in WP Crontrol (I'd rather find the root cause in WordPress) but I suspect I'll need to because it's an issue thats difficult to spot unless you're actively monitoring your site.

[szepeviktor]

I also see this in cron output.