Yeah, I agree with your points, I never liked these scaled answers either. The biggest problem I see it that answering 0 could be just “I don’t know and I don’t care” but it could also be “I think there’s no problem at all”.

On top of that, it was a bit harder for me to decide on how to translate what OP translated as “concern”. The verb used in Slovak, “trápiť”, feels a tiny bit harsher to me. It’s still most likely the closest translation - we also use it as to “worry”, but in general “trápiť” means causing (mental or physical) pain. I think it’s possible that some people understood it a bit more closer to English “suffer”.