APEX 5 Rejoin Sessions
In APEX 5, when Rejoin Sessions is set to Enabled for All Sessions. If you are coming from a non-public page, go to a public page, and go back to a non-public page it will break your session and require you to login again.
No parameters are being passed in the links, embed in frames is set to Allow from same origin. According to the description of the feature, it should be re-using the sessions. As it is when an applications use both public and non-public pages, users are required to login multiple times.
I'd set all pages to non-public if it was an option, but we have some users who do not have usernames, and can't have access to some pages.