One unused attribute won’t allow itself to be ignored

I’m trying to get the data map to work right. Problem is that I when I remove fields from the import sample file, those fields don’t go away from the data map, even if I mark them as inactive and save, close, and open later.

I’ve got one custom attribute “Region” in particular that keeps showing up as unmapped, even though I keep marking it as “ignore”.  I’ve got other fields that stay ignored, but this one just won’t.