Just an idea, have you checked if there changed something in the rights management? In the past I had sometime the feeling that setting are changing after an update back to the default value (no proof, just a feeling)
thank you very much for your quick answer.
I am sorry and feel a little ashamed to bother you with this obviously documented matter, I managed to find it myself in german KB.
I was just looking into english mutation https://kb.i-doit.com/en/basics/custom-counter.html which states just tbd. I myself would find it useful, if empty kb articles contained at least a ling to their german counterparts, as using translator is much easier for me than trying to find out what to search for in language I do not use fluently.