Hi Imtiaz, thank you for your reply and great that you are looking into it.
In the meantime – unfortunately for the debug but fortunately for me – my client has changed the structure of their site so both tabbed content blocks are not live anymore. In case it’s a general issue, I am happy to help solve it nevertheless, of course. Perhaps I can grant you access to the disable pages somehow, if needed. Also the dev site still exists, although, as mentioned, the problem was not occuring there.
Kind regards
Matthias