While trying some bundles from the sa team we find errors in v4 saying

Template "@ezdesign/viewbase_layout.html.twig" is not defined.

To reproduce the issue you can try to add following controller

<?php

namespace App\Controller;

use eZ\Bundle\EzPublishCoreBundle\Controller;

class DefaultController extends Controller
{
    public function test()
    {
        return $this->render('@ezdesign/viewbase_layout.html.twig');
    }
}

Assign a path for it and try it. you should see a symfony exception like in the pic.

If you do the same with 3.3.12, there's no error at all.