I use custom views a lot, and when selecting a new captain, I use a custom view in the Captain subsection of the Tactics screen. However, when I use this screen, no matter which player I drag across, the captain is always Paolo Maldini.
Playing as Platense in Argentina, Noah Mavrommatis is Argentinian/Greek/American, but in my custom view he is displayed as Argentinian/Argentinian. This isn't a problem with Ramiro Gonzalez (Argentinian/Chilean) or Sasha Marcich (Argentinian/Italian), so I assume that it's a bug with him having three nationalities.