Google web font imports breaking with advagg
You'll want to follow this issue https://www.drupal.org/node/2396609 Inline critical css

I'm guessing you're using the "Inline CSS on specific pages" setting on the AdvAgg: Modifications page. If the imports and not working correctly when everything is inlined, please open up a bug report explaining this with a good way for me to reproduce the issue locally.

Also noted that you can use the Adjust CSS location and execution setting to load the css async without having to mess with the tpl file.