Threads after reading still show as unread
 

When viewing all the threads in the a particular forum, you click to view the thread and then go back, that particular thead should be not bold, as being read. But for some reason there are some posts that do not show up being read even after viewing it. Is there a setting somewhere or is this a bug?

We did move some threads from one section to another and not sure if that would have something to do with it. But it looks like even if you make a new post and go back sometimes it still doesn't show being read.

Thanks for your help.