"Add nested all/none selection" works in opposite direction

I'm using a view which displays nodes according to what's checked in the better exposed filters on the left. The objective is to have the nested terms selected when their parent term is selected.

However, the opposite takes place: when I check the parent item, nothing would happen. When I uncheck the parent, all of its children are automatically checked. So it works the other way. What could be causing this odd behaviour, and how can I fix this please?

Attached you can find my view (if it could provide any insight at all).