My issue is similar to this, but, for my users, the Unauthorized page is reached when selecting the category from an Overview page's widget (giving the URL: ".../community/end-user/content?filterID=contentstatus%5Bpublished%5D~category%5BAccount%2B%2526%2BContact%2BManagement%5D". However, when accessing the same category from the Activity page's tile or from the content page itself, the URL is ".../community/end-user/content?filterID=contentstatus%5Bpublished%5D~category%5Baccount-contact-management%5D"
I see that you created a case in your private support group but I wanted to follow up here for others with the same question. It was discovered in your case that you are running into the bug JIVE-67732
JIVE-67732 - An encoding change causes existing links to break when the URL contains an encoded space. This issue is prone to break links to content that is filtered by category, and can result in unexpected "Access to this place or content is restricted" messages
This will be fixed as part of the maintenance release on March 4th.
I also wanted to provide a list ofKnown & Fixed Issues in Jive-n and Jive-x Current Release (2016.3)
Hope this helps.