Expandable text box works but text has a bug

Hello, I have got a problem and would be very happy if anybody could help me:

I use an expandable text box with “show more” “show less”, I followed the tutorial - it works but there is a problem with the content of the text: the german umlauts of the text do not appear as provided (example: " der allgegenwärtig ist" → " der allgegenwärtig ist" . . Pls check these sceenshots:


Here the result in preview and published mode:

What can I do? Thank you very much! Best regards,Anna-Sophie