Dropdown missing one item and format

Hi,

I have a collection ‘Year’ where the items are:

Filter by Year
before 1980
2010 to 2020
1980 to 1990
2000 to 2010
1990 to 2000

And I’ve sorted them in the above order by using the ‘date create’ sort.

On the preview of the site the dropdown shows:

Filter by Year
2010-2020
2000-2010
1990-2000
1980-1990

Once I click any value, and open the dropdown again, the “Filter by Year” is gone.

I’m assuming it has something to do with the definition of the ‘Title’ field but I’ve tried all I could think of and couldn’t find the right setting.