Content Type "Interactive Videos" broken

In the content type: " Interactive Videos", the window does not look correct. Buttons are missing and the content is out of place. In the browser console, I get the following error message: The property "name" is missing in the field 0. (h5peditor.js:423:16) Do you have any idea where the problem could be. I can't find anything  about this

 H5P: 1.15.3

 Firefox: 93.0 64Bit

 Wordpress: 5.8.1

 Macbook Big Sur


Content types: 

In the meantime I deactivated all plugins and looked at the result. Unfortunately no change. Can it be that the server on which H5P is running does not get a connection to H5P? I'm not sure - found this link to my JS problem: 

After I changed the language for WP, the error was fixed.