Strange behavior with missing article text

Hello,
we have a weird behavior here with some articles. Although they are fully contained in the backend, as you can see at the estimated reading time, the body is not displayed.

What can this be? This only occurs with the current theme. I alread tried to deactivate plugins, but it changed nothing. When i switch to the basic theme, the article is shown correctly.

An example is: https://www.teilzeithelden.de/2017/03/13/rezension-das-schwarze-auge-ewiger-hass-ulisses-spiele/

Thanks for the help in advance
Roger