Following T335971, it appears the extension is saving preferences for temporary users.
Update the code to treat temporary users like anon users.
https://www.mediawiki.org/wiki/Extension:LDAP_Authentication
Wherever these do something different based on whether a user is anonymous or registered, they may need updating (including comments).
Tests and comments should also be updated.
Notes
To help with searching:
In PHP preferences are saved via UserOptionsManager::saveOptions
In JS preferences are saved via methods defined on options.js:
This extension is unmaintained - please investigate if it's worth updating.