I've seen this a few times. I come here, click the new posts topics on the pinned top bar, read the posts, then go to the main forum page and various categories show they have new posts. Click the new posts button, nothing there. Go to the main forum page (using the navigation tree, not the browser back button) and it still says new posts. Just did a nice loop five times or so to see if it would clear. It did not. Click on the board that it says there are no new posts, it opens showing indeed no new posts. Then go back to the main page and it's marked read.
SMF has this issue to from time to time. So it's very possible this is a long standing bug. Figured I'd report it anyway. Sadly a hard one to specifically trigger though.
If I remember right, this has something to do with sub-boards. SMF doesn't handle the unread posts in a sub-board too well from what I recall. If you click on the unread, and then click the all unread link on that page if there aren't any posts, it should clear it. It's something I think that was never addressed because of how complicated it could get, and how resources would be affected. That's the history I recall anyway. :)
That is the "usual" tricky problem of the "new" indicator for any board.
What Elk (and SMF) does is not tell you the board has unread posts, but just that you have not yet visited the board since new posts were made.
When this concept is clear, here it is what happens any time you visit a topic:
* if you open a topic from the board index (i.e. the "last message"), you get an url that looks like this:
the "boardseen" parameter ensures the board is "marked as read".
* when a topic is opened coming from any other source apart the board index the parameter is not added and the board is not "marked as read".
* of course if you enter the board, it is "marked as read" because you enter into it.
The problem is that is counter-intuitive in most of the cases.
On my forum a long time ago, I installed a mod that at each page load does quite a bit of ugly queries (in fact several of the queries from the unread/unreadreplies pages) just to determine if the any of the boards contain unread topics and if so it uses a special icon (instead of on/off/on2).
That would likely be the idea solution. Unfortunately, this may or may not be a problem, but I suspect it would be on forums with some traffic (mine is rather small-ish and low traffic ~100k posts).
It may be possible to add a column to log_boards (or log_mark_read) to remember the...number of unread topics in a board for a certain member? That should allow to have an easy way to know if a board has unread topics or not for a certain member.
I don't think this one is tracked yet for 1.1.6.
I *think* this has been fixed somewhere in 1.1. I *think*.
I guess it was here https://www.elkarte.net/community/index.php?topic=5186
I read and I don't think @Spuds
did properly fix that but I moved this to exterminated nonetheless.