Button in wrong position

On my German language learning site, I’m using GamiPress Buttons at the bottom of explanatory pages so that users can reward themselves after having read the explanation. The button is wrapped in WP-Members shortcode so that only logged-in users can see and access the button. Everything has been working fine for a long period on many pages.

Now suddenly on only one page
https://ondaz.de/zweiteilige-konnektoren/
the button appears as a long column on the right side of the page instead of at the bottom. The button is still active and delivering points when clicked.
For the time being, I have removed the button’s WP-Members wrapping on this particular page to make sure the problem is not caused by WP-Members and in order to allow you to inspect the problem without having to create an account. I cannot find any difference between this page and other pages where Button is displayed properly.

The page I need help with: [log in to see the link]