symfony 4.4 + FOSCKEditor + helios-agElfinder not working

Using Symfony 4.4 +"friendsofsymfony/ckeditor-bundle": "^2.2" +"helios-ag/fm-elfinder-bundle": "dev-master" after composer install (but also tried composer require helios-ag/fm-elfinder-bundle from the docs page) gives me

Executing script cache:clear [KO] [KO]Script cache:clear returned with error code 1!!  !!  In RegisterControllerArgumentLocatorsPass.php line 173:!!                                                                                 !!    Cannot determine controller argument for "FM\ElfinderBundle\Controller\ElFi  !!    nderController::load()": the $eventDispatcher argument is type-hinted with   !!    the non-existent class or interface: "Psr\EventDispatcher\EventDispatcherIn  !!    terface".                                                                    !!                                                                                 !!  !!  Script @auto-scripts was called via post-install-cmd

route is imported, config files set...

BTW: include_assets is not recognized in fm_elfinder.yml (commented it out)

I have absolutly no idea. Can anyone of you guys give me a clue?

PS: worked fine with symfony 4.1