So I created a game and then changed the Interface default language from English to German.
Then I saved the game, exited after a while and changed the language back to English from the main menu.
Loaded the game, still event announcements in German.
In the options the setting was still english.
Changed it back and forth from inside the save, no dicd.
Perhaps someone can look into how the strings are loaded?
Old ones in German are fine.
But newly generated ones should follow the language setting. Perhaps check once on file load or something.