The site title field in the Customizer is actually a core WordPress control – I wonder if there’s something going on in your installation, or if it’s a core WP bug when handling your language.
Have you asked around on the WordPress.org forum to see if anyone else has experienced something similar?
I did some google searches and seems like its a wordpress thing. Something in wp-config.php specifically define(‘DB_CHARSET’, ”); define(‘DB_COLLATE’, ”); .
Its much easier for me right now to change it in customizer than go in those files and maybe cause more damage. Will ask around and update here if i find a good solution that i understand.