getTotalPaid is always 9

I have the same issue...
Payments are marked as completed and paid, but the total amount remains open.
The order log shows that the payment info was received correctly.

Some quick debugging showed that the payment update from Mollie webhook is received in the "onNotify" function. The status is correct and this piece of code is executed:

    switch ($mollie_payment_remote_object->status) {
      case MolliePaymentStatus::STATUS_PAID:
        // Capture payment.
        $payment_transition = $payment->getState()->getWorkflow()->getTransition('authorize_capture');
        $payment->getState()->applyTransition($payment_transition);
        $payment->setRemoteState($mollie_payment_remote_object->status);
        $payment->save();
        break;

This correctly registers the payment as paid, but does not register the amount paid.
Looking through the commerce documentation: it states that it will only update the amount if the state changes to "completed", so this should work?

Do you need more info, I'm a bit lost in debugging this...