UBB.Developers Forums UBB.threads 7 Development How Do I? 6.5 marks all read randomly

has anyone else noticed this?
when entering a forum containing multiple threads with new answers, sometimes all are marked read after reading just one thread and returning to the index (not the main index).

I deleted my cookies and started fresh, but it still happens now and then.

It does it to me if in not logged in. If I am on as an anon it will show all posts as new. when I go into read one forum and come back, they are all marked read

it does to me when I'm logged in.
anonymous reading isn't possible because of group rights, you have to be logged in or you see nothing in my forums.

I have one user reporting this behaviour, maybe more to come. He goes into a board which says "no unread posts" (what is correct) and finds lots of "unread" marked messages. And vice versa. He already deleted all his cookies several times, but nothing changes.

Same here...must be a bug in 6.5