I have a CiviCRM (5.55.1) running on Drupal (9.4.8). The language ist set to German.
When I click "Neues Rundschreiben" aka "New Mailing", the URL of that menu item is https://MyHost/civicrm/a/#/mailing/new but then it redirects me to https://MyHost/de/civicrm/a/#/mailing/new. This give a Page not found error. If I remove the "de" from path, all works as expected.
This site does not use Mosaica and it does not have Multi-Language enabled.
It seems the only menu entry with this behavior.
Any Suggestion?