Is there a way to rename the MC?
One of the characters apparently uses a name I regularly use for the MC, so dialog can get confusing.
Save Editors are currently broken with RenPy 8.1, so I can't fix it using that.

There's only really one Male character with any significant content and that's the MC, so I'm interested to hear how this has happened?

Do you mean after you start the game?

Yes, Fernando's name is just a variable you can change in the script. Search for whatever you named him and edit the variable.