- Tested on Drupal7
- Enable locale/i18n and two languages (ex: English and French)
- Enable language-prefix language detection
- In CiviCRM, enable multilingual, and two languages
Then use the Drupal language switcher to change the language.
Result: the language only changes if we flush the CiviCRM cache. This is because the cache-flush removes data from
civicrm_cache, including some session data.
Bug happens since 5.29, also in 5.30 and master.