I've checked the configuration, the page source and the console, but I could not find any errors.
Then I remembered I had a tag assistant extension available by google, which tells you if there are issues with the analytics tracking code. When I run the extension on your page, I see this error: https://i.imgur.com/fE89lNc.png
Missing analytics.js script
Which is weird, because I can see the analytics integration code, although it looks a bit different from the recommended one here: https://goo.gl/Nl5HK
My guess is that during the page load something either unloads/changes this script. I honestly don't know.Best,
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