Batch operation keeps looping after completion
I was able to fix it by using the magic send() method for RedirectResponse class and building a full URL (mostly) manually.

  public static function completeImport() {

    $url = $GLOBALS['base_secure_url'];
    $url .= $GLOBALS['base_path'];
    $url .= Url::fromRoute('system.admin_content')-&gt;getInternalPath();
    $url .= '?status=All&amp;type=academy_webinar&amp;title=&amp;langcode=All';

    $redirect = new RedirectResponse($url);

    $redirect-&gt;send();
  }