Jordan Rich

Hi there @fotske we certainly want to look into this issue with Action Scheduler

To begin, could you please provide us with your store URL? Additionally, please ensure that Remote Diagnostics is turned on in the plugin Advanced settings, that can view your store’s status in our internal tooling for a more detailed investigation.

To help us narrow down the cause, we also highly encourage performing a temporary plugin conflict audit. If possible, try disabling all plugins except for your critical setup: WooCommerce and Mailchimp for WooCommerce.

Ideally, this is best tested in a staging environment so your live store isn’t affected. We completely understand if setting up a staging site isn’t feasible with your current hosting arrangement, but if it is an option for you, it would give us a completely clean baseline to rule out any third-party conflicts triggering these repetitive synchronization loops.

I’ll address each of your questions below:

What exactly triggers MailChimp_WooCommerce_Single_Order actions?

1. Order status changes – When an order moves from pending to processing/completed
2. Order saves – Direct saves in WooCommerce (admin or frontend)
3. Block checkout – Orders placed via WooCommerce Blocks (with 15-second delay)
4. Partial refunds – When an order is partially refunded
5. Full sync – During bulk sync operations
6. Manual resync – When admin triggers a manual order resync

Each trigger sets different flags like is_admin_save, is_full_sync, or partially_refunded to control how the order is processed. Most triggers queue the job asynchronously via Action Scheduler, except manual resyncs which execute immediately.

Why would more than 51,000 such actions be generated for a store with only 4,558 orders?

We’re not sure this is why we’ll need to try to investigate further by attempting to replicate a store with 4k+ orders. It could be Repeated Hooks on Order Save or our Retry Logic or something else it’s difficult to say without example logs.

Does Mailchimp periodically re-sync all orders or customers?

No, the plugin doesn’t automatically schedule periodic resyncs. Full syncs are only triggered manually by the user such as; Initial Setup or a Manual Force Resync

Could there be a configuration issue causing repeated synchronization of the same orders?

Quite possible in order find out for sure, once we have the store URL and view it in our internal tooling we’ll be able to view errors and logs to see if it points to any configuration issues. Also here’s where a plugin audit also could be helpful.

Is this amount of Action Scheduler activity considered normal?

This is not normal and speaks to either a conflict with Action Scheduler between a plugin or process. Again we’ll find out more as we investigate.

Is there a recommended cleanup or optimization procedure?

Yes for optimization in some cases we recommend the Advanced Queue Setup in CLI Mode (https://github.com/mailchimp/mc-woocommerce/wiki/Advanced-Queue-Setup-In-CLI-mode)

This setup relies on Action Scheduler, but completely decouples it from default WordPress behavior for sync.

By disabling the default runner and executing tasks via a system cron job (crontab), your store processes syncs automatically in the background every minute. This eliminates the reliance on both wp-cron.php and live web traffic to trigger the queue.

It’s our pleasure to assist, looking forward to your reply with more details so we can find a resolution.

Greetings @rtpharry We currently have a filter that accomplishes this. Please add the following to your functions.php file for the active theme on your WordPress site.

add_filter('mailchimp_checkout_opt_in_options', 'edit_checkout_opt_in_options');
function edit_checkout_opt_in_options( $options ) {
    $options[] = [ 'label' => esc_html__( 'Hidden, unchecked by default', 'mailchimp-for-woocommerce' ), 'value' => 'hide' ];

    return $options;
}

Once the filter is added to the file and updated you’ll see an additional UI feature when the Mailchimp newsletter block is selected in the Site Editor as seen in the following screenshot in google drive : https://drive.google.com/file/d/1IczVaNRc3gm0ORJW4jw7lNAKi4tI3d1Z/view?usp=sharing