I have the same problem I think.
I have medialibrary pro. It works brilliantly (great extension by the way!) when in Legacy mode. However, when I turn legacy off, all works as normal UNTIL I try to view an individual item from the library, for example a specific book. Instead of showing the book details, the page is blank and at the top it says the category title, the title of the book and then on the line beneath: "Restricted Access".
If I have legacy mode on then it works fine.
Any suggestions gratefully received.