We upgraded to Moodle 3.3.1+ this summer and are using Office 365 SSO plugins. Alls our users are SSO users and since the upgrade, no matter what, when they login their language preference gets reset to 'en'.
I have manually changed the language to 'nl' via a database query, but since the change happens on login, when they login their language gets reset back to 'en'. This did not happen in our previous version (3.1) where we also userd the SSO plugin through Office365.
Has anyone got any idea on where to look? I can start digging through the source code, but maybe someone can tell me if there is a piece of code that changes the language according to some settings in Office365?