Symfony - Inject Session Flash Bag into Service with output and translation in TWIG via app.session

config.yml

services:
    app.bundle.service:
        class:  AppBundle\Service
        arguments:
            - "@doctrine.orm.entity_manager"
            - "@security.token_storage"
            - "@session"
            - "@translator.default"

Controller.php

<?php

use Symfony\Bundle\FrameworkBundle\Controller\Controller;

class DefaultController extends Controller
{
    /**
     * @Route("/")
     * @Template()
     */
    public function indexAction($type)
    {
        $data = $this->getRequest()->request->all();

        $service = $this->get('service');
        $service->setData(array('quantity' => 1));

        return $this->render('AppBundle:Default:new.html.twig', array());
    }
}

dormer_calculation.de.yml

Setting initial window surface to %window_surface%².: Setze Fensterfläche auf %window_surface%²

index.html.twig

{% for flash_message in app.session.flashbag.get('notice') %}
    <div class="flash-notice">
        {{ flash_message }}
    </div>
{% endfor %}

Service.php

<?php

use Doctrine\ORM\EntityManager;
use Symfony\Component\Security\Core\Authentication\Token\Storage\TokenStorageInterface;
use Symfony\Component\HttpFoundation\Session\Session;
use Symfony\Component\Translation\Translator;

class Service
{
    private $entityManager;

    private $tokenStorage;

    private $session;

    private $translator;

    private $translationDomain = 'foo';
    
    public function __construct(EntityManager $entityManager, TokenStorageInterface $tokenStorage, Session $session, Translator $translator)
    {
        $this->entityManager = $entityManager;
        $this->tokenStorage = $tokenStorage;
        $this->session = $session;
        $this->translator = $translator;
    }
    
    public function addMessage($message, array $parameters = array(), $type = 'notice')
    {
        $this->session->getFlashBag()->add(
            $type, $this->translator->trans($message, $parameters, $this->translationDomain));
    }

    public function getMessages()
    {
        return $this->session->getFlashBag()->all();
    }
    
    private function setData($data)
    {
        $windowSurface = 360;
        
        $this->addMessage("Setting initial window surface to {{ window_surface }}&sup2;.", array(
            '%window_surface%' => $windowSurface));
    }
}

I think I found the problem @adampiotrowski:
The Flash Bag can only be outputted once!? As soon as you dump it somewhere before the twig template, it will be emptied.

Can this setting be changed? Should it?