Error: Page requires additional network round trips

Hey there,

first of all: thank you for your great plugin! Our AMP pages already work really well. However, running our pages through Google’s PageSpeed Insights Tool, we encountered an error concerning the above-the-fold content:

“Prioritize visible content

Your page requires additional network round trips to render the above-the-fold content. For best performance, reduce the amount of HTML needed to render above-the-fold content.

The entire HTML response was not sufficient to render the above-the-fold content. This usually indicates that additional resources, loaded after HTML parsing, were required to render above-the-fold content. Prioritize visible content that is needed for rendering above-the-fold by including it directly in the HTML response.

None of the final above-the-fold content could be rendered even with the full HTML response.”

Do you – by any chance – know what exactly could be responsible for this error? Here is a link to the pagespeed analysis of the index page of our blog:
https://developers.google.com/speed/pagespeed/insights/?hl=en&url=https%3A%2F%2Fwww.camperdays.de%2Fblog%2F%3Famp