Not receiving new order e-mails -> payment not processed?

Sometimes, we do not receive an e-mail from WooCommerce that a new order arrived. The payment however was succesful (as in, we got an e-mail from Mollie that we received a payment). It seems like there is no callback to WooCommerce that the payment was processed succesfully.

This issue seems very similar to https://wordpress.org/support/topic/paid-orders-not-always-processed-in-woocommerce/. Started around the same time as well (a couple of weeks ago).

Relevant log output (X’out some stuff):

2025-11-06T20:32:14+00:00 DEBUG ideal: Start process_payment for order 6717 CONTEXT: [true]
2025-11-06T20:32:14+00:00 DEBUG Creating payment object: type Payment, creating a Payment.
2025-11-06T20:32:14+00:00 DEBUG  Order 6717 returnUrl: https:/xxxxxxxxxx/checkout/order-received/6717/?key=wc_order_xxxxxxxxxxxx&order_id=6717&filter_flag=onMollieReturn CONTEXT: [true]
2025-11-06T20:32:14+00:00 DEBUG  Order 6717 webhookUrl: https:/xxxxxxxxxx/wp-json/mollie/v1/webhook CONTEXT: [true]
2025-11-06T20:32:14+00:00 DEBUG {
    "amount": {
        "currency": "EUR",
        "value": "XXX.XX"
    },
    "description": "Bestelling 6717",
    "redirectUrl": "https:/xxxxxxxxxx/checkout/order-received/6717/?key=wc_order_xxxxxxxxxxxx&order_id=6717&filter_flag=onMollieReturn",
    "webhookUrl": "https:/xxxxxxxxxx/wp-json/mollie/v1/webhook",
    "method": "ideal",
    "issuer": "",
    "locale": "nl_NL",
    "dueDate": "",
    "metadata": {
        "order_id": 6717
    }
}
2025-11-06T20:32:15+00:00 DEBUG ideal: Mollie payment object tr_XXXXXXXXXXXXXXXXXXXXXX (live) created for order 6717
2025-11-06T20:32:15+00:00 DEBUG For order 6717 redirect user to Mollie Checkout URL: https://pay.ideal.nl/transactions/https%3A%2F%2Ftx.ideal.nl%2F2%2XXXXXXXXXXXXXXX?sig=XXXXXXXXXXXXXXXXXXXXX
2025-11-06T20:34:05+00:00 DEBUG mollie_wc_gateway_ideal: Mollie payment object tr_XXXXXXXXXXXXXXXXXXXXXX (live) action call for order 6717.
2025-11-06T20:34:05+00:00 DEBUG Mollie\WooCommerce\Payment\MollieOrderService::orderNeedsPayment mollie_wc_gateway_ideal: Order 6717 orderNeedsPayment check: yes, order not previously processed by Mollie gateway. CONTEXT: [true]
2025-11-06T20:34:05+00:00 DEBUG Mollie\WooCommerce\Payment\MolliePayment::onWebhookPaid called for payment 6717
2025-11-06T20:34:10+00:00 DEBUG Mollie\WooCommerce\Gateway\MolliePaymentGatewayHandler::getReturnRedirectUrlForOrder 6717: Determine what the redirect URL in WooCommerce should be.
2025-11-06T20:34:10+00:00 DEBUG Mollie\WooCommerce\Payment\MollieOrderService::orderNeedsPayment mollie_wc_gateway_ideal: Order 6717 orderNeedsPayment check: yes, order not previously processed by Mollie gateway. CONTEXT: [true]
2025-11-06T20:34:11+00:00 DEBUG Mollie\WooCommerce\Payment\PaymentModule::onMollieReturn: Redirect url on return order mollie_wc_gateway_ideal, order 6717: https:/xxxxxxxxxx/checkout/order-received/6717/?key=wc_order_xxxxxxxxxxxx&utm_nooverride=1
2025-11-06T20:35:07+00:00 DEBUG mollie_wc_gateway_ideal: Mollie payment object tr_XXXXXXXXXXXXXXXXXXXXXX (live) action call for order 6717.
2025-11-06T20:35:07+00:00 DEBUG Mollie\WooCommerce\Payment\MollieOrderService::orderNeedsPayment mollie_wc_gateway_ideal: Order 6717 orderNeedsPayment check: yes, order not previously processed by Mollie gateway. CONTEXT: [true]
2025-11-06T20:35:07+00:00 DEBUG Mollie\WooCommerce\Payment\MolliePayment::onWebhookPaid called for payment 6717
2025-11-06T20:35:07+00:00 DEBUG Mollie\WooCommerce\Payment\MolliePayment::onWebhookPaid WooCommerce payment_complete() processed and returned to Mollie\WooCommerce\Payment\MolliePayment::onWebhookPaid for payment 6717
2025-11-06T20:35:07+00:00 DEBUG Mollie\WooCommerce\Payment\MolliePayment::onWebhookPaid processing paid payment via Mollie plugin fully completed for order 6717

-> this is me, updating the order to status "processing" manually, the next day:

2025-11-07T10:45:07+00:00 DEBUG Mollie\WooCommerce\Payment\PaymentModule::shipAndCaptureOrderAtMollie - 6717 - Try to process completed order for a potential capture at Mollie.
2025-11-07T10:45:07+00:00 DEBUG Mollie\WooCommerce\Payment\PaymentModule::shipAndCaptureOrderAtMollie - 6717 - Payment already completed at Mollie, can not be captured.