Some letter combinations fail in lists

To reproduce, go to the user directory and under the profile of a contact in the list, click on the edit, to add the contact to some lists, comma or space separated. Following letter combinations are saved but not visible on saving (still says "(none)": za, sd, us ... when clicking to edit, the letters are still there. Its not an issue of country codes not being accepted as lists, because au, ru, eu, and others, work fine. All letter combinations, short and long, should be allowed, but only some are failing.