Tracking details not updating via eBay's API

I am currently trying to send information to eBay to set the orders shipment/tracking details. At the moment I am getting a 'success' message but no information is update on eBay's website.

I have been using the links below to guide me on implementing this change:

http://developer.ebay.com/devzone/large-merchant-services/Concepts/MakingACall.html

http://developer.ebay.com/devzone/merchant-data/CallRef/SetShipmentTrackingInfo.html#Samples

The format of the XML I am sending back is in the exact format as described, please see below the details I am sending and the PHP used to send via CURL through eBay's API.

XML:

<?xml version="1.0" encoding="UTF-8"?>

    <BulkDataExchangeRequests>
        <Header>
            <Version>591</Version>
            <SiteID>0</SiteID>
        </Header>
        <SetShipmentTrackingInfoRequest xmlns="urn:ebay:apis:eBLBaseComponents">
            <OrderID>261671515555-0</OrderID>
            <OrderLineItemID>261672341232</OrderLineItemID>
            <Shipment> 
                <ShipmentTrackingNumber>JD0002250296232332</ShipmentTrackingNumber>
                <ShippedTime>2014-11-27T14:41:27\Z</ShippedTime>
                <ShippingCarrierUsed>Yodel</ShippingCarrierUsed>
            </Shipment>
        </SetShipmentTrackingInfoRequest>
    </BulkDataExchangeRequests>

PHP:

    $xml_request = "";
    $connection = curl_init();
    curl_setopt($connection, CURLOPT_URL, $ebay_url);
    curl_setopt($connection, CURLOPT_SSL_VERIFYPEER, 0);
    curl_setopt($connection, CURLOPT_SSL_VERIFYHOST, 0);
        curl_setopt($connection, CURLOPT_HTTPHEADER, $headers);
    curl_setopt($connection, CURLOPT_POST, 1);
    curl_setopt($connection, CURLOPT_POSTFIELDS, $xml_request);
    curl_setopt($connection, CURLOPT_RETURNTRANSFER, 1);
    $response = curl_exec($connection);
    curl_close($connection);    
    var_dump($response);

The issue was the provider of the API was having intermittant issuses.