Mapping dropdown using monday for subitems

I have an existing scenerio where if a subitem in monday changes it will change the parent item too to the same status.

I want to change it so if a parent item dropdown column changes, it will change the subitems as well.

How can i do it? right now i’m getting an error that there is no parent item.
I think it may be because i am bringing the sub item before the parent, but i’m not sure how to reverse it.

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