Slides show files as anonymous user

I have set up a views slideshow of mixed content (videos and images). The slideshow is showing files rendered as "slideshow", which is a view mode created with display suite.

So i have one big slide where either the big images or the video player shows. Under the slide i have the controls of thumbnails.

Everything works just fine when using the slideshow as admin user. I click on the preview controls and the full content shows as slide.

As anonymous user this thing is acting weird. I click on a preview and for a brief moment the slide appears but right after that drupal is redirecting to the file itself (e.g. www.example.com/file/14598).

Insepcting the source code I see some major difference. As anonymous user the thumbnail ist wrapped in an a tag linking to the file while as admin user the a tag is rendered above the thumbnail without any content.

Any idea where to look?

Thx