According to https://groups.google.com/a/opencast.org/forum/#!topic/anwender/YFKpOzi7YNA and https://groups.google.com/a/opencast.org/forum/#!topic/users/i1BFLsYT_GM, unprivileged users (no ROLE_ADMIN) cannot view media package element details on Recordings->Events->"Event Details">Assets>Media.
The reason is that the Sprint Security configuration is missing some rules required by those views to access the backend functionality.