H5P Image Juxtaposition Content does not appear on browsers like Firefox and Google Chrome

Hello,

I've been working with H5P for a long time, it's the first time this problem has come up. Different people in different countries have tested the site on several browsers. H5P content is not displayed on Firefox and Chrome desktop browsers.

I am grateful for any help!

Detailed steps to reproduce the bug (exactly how and when did it happen): H5P Image Juxtaposition Content does not appear on browsers like Firefox and Google Chrome on multiple devices, it only works good on Safari and Opera
http://birds.cadmos.de/doppelgaenger-schnell-und-einfach-unterscheiden/ 

1. Platform and version number. E.g. Drupal, Wordpress, Moodle: Wordpress
2. Mobile or Desktop: Mostly Desktop, sometimes on mobile too
3. Browser: Chrome, Firefox, Safari etc: Problem with Chrome Desktop, Firefox Desktop, Chrome on Samsung mobile devices 
4. H5P plugin version: Version 1.15.0
5. H5P content type and version (if a content type was used), and a sample URL or attached H5P. Image Juxtaposition 1.4.1
6. Any browser console errors: Content does not appear on browsers like Firefox and Google Chrome on multiple devices
7. Any PHP errors
8. Screenshots if it's a visual problem: Screenshots show that it does not appear on Firefox and Chrome but it is shown on Safari
9. Any recent changes to the environment (new plugins/modules, updates, configuration changes etc.): No, different people tested it and all had the same problems on different devices
10. Any recent changes to the browser you're using (new extensions, updates etc.): No, different people tested it and all had the same problems on different devices