I have just tried it, and it's both thread I have read before (which go to the latest unread post but it's in the middle of the post so I can't read the beginning of it!), as well as new posts I have never read before, which goes to the first post as the pictures show, but at the middle or end of the post so I can read the beginning of the message.
Also since i have you, I see two other problems that I'll share here - I can't post in a new thread for some reason, I click on post new thread, it lets me, it lets me add a title, but the body of the message text box never starts a cursor to start typing - and if I type nothing happens. I thought it was something with consecutive posts as I had just added this thread, but I have 300+ posts. I add this problem here since I can post a new thread for some reason.
Also - if a user does Tools/Mark forum read, it does not refresh the thread list to show all threads as read now. The old forum site used to do that. I find myself wondering if the "Mark forum read" command worked or not, I have to manually refresh the browser page to see the result.