Hi Chris,
Thanks for your comments about the "uniquely secured content" issue. Per your description, I understand the permission has been set up properly, however when administrator click "show uniquely secured content", there is nothing happens.
I would like to confirm if this issue can be reproduced in another browser? It also could be an add-ones compatibility issue. I'd like to suggest you disable all 3rd-party add-ones in IE to verify if the issue persists.
Microsoft values your feedback, I will continue to monitor this thread for a few days and will reply to any additional posts or questions.
Thanks,
Allen Qiu