Hhm seems we still have some old untranslated text fields
1.) Open the co payment calculator and click on the arrow
2.) Change the content of the text box “Spieler” from the wrong player name to the correct one
3.) Click on “copy values”
4.) Paste it into a message and look if it contains the correct name
5.) Reload the game (F5) and look if the player name has been saved permanently