When on a page and expanding a folder next link is a 404

I have a website I built that has both public and private areas. Some documents are public and others private. As well some pages are locked as private and I have used a user role editor to allow the user level subscriber to see private pages.

When you go onto a private page that has a MD folder on it and then go to another private page everything is fine. When you however expand a folder to show the files, the next link you select, if a private page, gives a 404 error as if your session has been logged out. Refreshing the screen shows the page however, so the session has not been logged out.

IF you are logged in as admin this problem does not occur. only if logged in as subscriber.

Any thoughts? I wish I could show you the link but it’s in the private area of the site that is currently live.