I had "ready for scheduling" on 8 July. I used my Euro birth certificate which shows everything as I always knew, and as accepted by KCC. However, when I dug into my late father's documents I found an Asian birth registration with an apostilled/certified name change affidavit. I learned I was registered in two countries' birth registries, due to the my parents' different nationalities. Apparently, my birth name was changed per Asian newborn traditions, and subsequently my later Euro registration only shows the new name. I was unaware, since every ID I ever held shows the current name.
Nonetheless, it transpires I had an official name change (albeit it as newborn). I wanted to add this on DS-260 for accuracy, under "former names" on 16 July. Maybe it triggered a name check or something. Conclusion is that KCC considered it too late, and replied the DS_260 will not be unlocked. What's worse (and a little unexpected) further processing will also be stopped and no interview will be scheduled as a result. As such, this means DV-2019 has concluded for me! No processing via embassy either, which might otherwise have happened if I was scheduled. Maybe I should be thankful I got spared interview/doctor's fees since there's no telling the embassy would've responded well either! Anyway, I guess I can try my luck in the future and avoid the issue. Thanks to you all I got even this far, the DV-process was quite a mystery before I reached these resources.