My application keeps loading after trying to clear FilesystemCache

I have an application that runs on Symfony 4. I use the filesystem cache component. I wanted to create a function that empties it, but unfortunately, my entire application is now broken. All pages will continue to load forever.

Below the script that I have executed:

<?php

namespace App\Controller\Admin;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\Cache\Simple\FilesystemCache;
use Symfony\Component\Routing\Annotation\Route;
use Symfony\Component\HttpFoundation\Request;

use App\Entity\Instelling;

class AdminInstellingController extends AbstractController
{
    /**
     * @Route("/beheer/cache-clear")
     */
    public function clearCache()
    {
        $cache = new FilesystemCache();
        $cache->clear();

        $this->addFlash("success", "De <strong>CRM DataServer</strong> cache is succesvol geleegd.");
       // return $this->redirect('/beheer/dashboard');
    }
}

I have deleted my var/cache folder, my temp folder where this cache is stored by default (sys_get_temp_dir), reinstalled my vendors, emptied my cookies and cache and restarted my computer. Nothing works at all and the application keeps loading. What do I have to do to resolve this?