Double sending response from 'affirm/payment/confirmAction'

[DianaSol]

We've faced up with this error:

2020-04-23T07:26:04+00:00 DEBUG (7): after getOrderPayment 
2020-04-23T07:26:04+00:00 DEBUG (7): affirm
2020-04-23T07:31:53+00:00 DEBUG (7): HEADERS ALREADY SENT: \<pre>[0] /home/budsies/website/app/code/core/Mage/Core/Controller/Response/Http.php:52
[1] /home/budsies/website/lib/Zend/Controller/Response/Abstract.php:779
[2] /home/budsies/website/app/code/core/Mage/Core/Controller/Response/Http.php:84
[3] /home/budsies/website/app/code/core/Mage/Core/Controller/Varien/Front.php:184
[4] /home/budsies/website/app/code/core/Mage/Core/Model/App.php:365
[5] /home/budsies/website/app/Mage.class.php:655
[6] /home/budsies/website/index.php:82
\</pre>

It appears after order confirmation at the Affirm side.

After some debugging, it turned out, that Affirm observer Affirm_Affirm_Model_Order_Observer_AfterSaveOrder sends the response prior to Magento.

The fix was - to remove sending response from the observer:

    public function postDispatchSaveOrder($observer)
    {
        $response = $observer->getControllerAction()->getResponse();
        $session = Mage::helper('affirm')->getCheckoutSession();
        $serializedRequest = $session->getAffirmOrderRequest();
        $proxyRequest = unserialize($serializedRequest);
        $checkoutToken = Mage::registry('affirm_token_code');
        $lastOrderId = $session->getLastOrderId();
        //Return, if order was placed before confirmation
        if (!($serializedRequest && $checkoutToken) || !Mage::helper('affirm')->isXhrRequest($proxyRequest)
            || !$this->_isAffirmPaymentMethod($proxyRequest) || !$lastOrderId) {
            return;
        }

        $session->setPreOrderRender(null);
        $session->setLastAffirmSuccess($checkoutToken);
        $session->setAffirmOrderRequest(null);
//        $response->setRedirect(Mage::getUrl('checkout/onepage/success'))->sendResponse();
        $response->setRedirect(Mage::getUrl('checkout/onepage/success'));
        return;
    }