Tab Content not shown in Conditional Region

I have a Tab Content within a Conditional Region. All contents are initially closed. The Nav List is outside of the Conditional Region. Now I have the problem, that the Tab Content is not shown on the first click of a Button. I have to click on a second Tab Button to make it appear.

I remember that there was already a topic on this issue but can’t find it. It was something because of the DOM not rendering.

Can someone give me a hint?