90% tracking loss in thank you page (ecommerce and page view)

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Name of affected component: Web Tracking (analytics.js)

Issue summary:
Since June 15 we are losing about 90% of the tracking of our thank you page, 
both ecommerce and page view, while our sales have remained at normal levels. 
Our last code release was on June 10. When a purchase is completed and the 
thank you page is shown we can see that ecommerce and page view pixels are 
requested with a 200 status code using Fiddle or Chrome developers tools but 
only 1 of every 10 pushes are reflected in Analytics dashboard.

This is our code:

<script type="text/javascript">

    (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
        (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
        m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
        })(window,document,'script','//www.google-analytics.com/analytics.js','ga');

     // Create the tracker
    ga('create', 'UA-2313997-8');

    // Fire off a pageview
    ga('send', 'pageview');

    // Include the ecommerce plugin
    ga('require', 'ecommerce', 'ecommerce.js');

    // Initialize the transaction
    ga('ecommerce:addTransaction', {
                 id: 'PX-4925-3611-2167', 
        affiliation: 'POINX S.P.A.',
            revenue: '19',
           shipping: '0.0',
                tax: '0.0'
    });

    // Add a few items
    ga('ecommerce:addItem', {
              id: 'PX-4925-3611-2167',
             sku: '551964f6e4b08be58405aec0',
            name: 'Yoga o Lightinbody',
        category: 'sport',
           price: '19',
        quantity: '1'
    });

    // Send off the transaction
    ga('ecommerce:send');
    ga('ecommerce:clear');

</script>

URL of the page exhibiting the issue: thank you page after every purchase

Steps to reproduce issue:
1. Complete a purchase flow
2. Check tracking is done correctly
3. Check Analytics dashboard

Expected output:
What do you expect to see after performing the above steps?
I expect to see the page view and ecommerce tracking in Analytics dashboard

Actual results:
What do you actually see after performing the above steps?
I only see the tracking of a 10% of our purchases.

Notes:
Our track Id is UA-2313997-8

Here you are a couple of Analytics dashboard screenshots showing the drop form 
average level to almost 0.
Original issue reported on code.google.com by oscar.ma...@gmail.com on 23 Jun 2015 at 5:59
Attachments:
alooi14 / analytics-issues

90% tracking loss in thank you page (ecommerce and page view) #675
