symfony 4.4 + FOSCKEditor + helios-agElfinder not working

Question

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? Thanks.

ps. worked fine with symf. 4.1