404 on thumnails

Image thumbnails always give me a 404. Cockpit is installed on a sub-folder → cockpitCMS. I’ve added the follow config to NGINX:

location /cockpitCMS/assets/thumbnail {
try_files $uri $uri/ /cockpitCMS/index.php$is_args$args;
}

Video thumbnails are working though!

Any idea what might be causing this?

Thanks in advance.

Have you tried GETting the file?