Hello,
I think this is happens when the topic and the topic author is deleted but the topic link is shared and still available on an other topic so that is still exist and clickable. When you click it this page comes. I believe there should be some errors related with this in /logs.
Edit: Now I cannot reproduce it but It happened once on our forum. A new userA create a topic, userB share that topic in other topic. Than userA is delete himself so the previously created topic is also deleted. After this when click the link what userB shared get this error page. But maybe it caused by a plugin for us 
Do you have any error in console or /logs?