Loading failed for the <script>

Hey there,
after uploading a test installation for a new project, I can’t reach the panel. Instead, the console’s giving me this (along with some ‘you know, wrong mime type, but we kindly loaded it anyway’ warnings):

Loading failed for the <script> with source “your-url.com/media/panel/b1179856b0372cb8777975cb658548ac/js/app.js” + plugins.js also, and vendor.js, too.

How would I even be debugging this?

PHP: 7.3
Kirby: 3.1.3

My file structure: index.php inside public, from there it goes like this:

<?php

include '../vendor/autoload.php';

$kirby = new Kirby([
  'roots' => [
    'index'    => __DIR__,
    'base'     => $base    = dirname(__DIR__),
    'site'     => $base . '/site',
    'content'  => $base . '/content',
    'storage'  => $storage = $base . '/storage',
    'accounts' => $storage . '/accounts',
    'cache'    => $storage . '/cache',
    'sessions' => $storage . '/sessions',
  ]
]);

echo $kirby->render();

Locally (docker), everything’s fine …

After installing v3.1.4, it disappeared …