Have had a quick search for this and not found anything.
If I'm reading on my iPhone and press the back button it will take me back a few days e.g. I'll go back to a sub-forum and the topics will be in the order they were a few days previously and if I hit the "new" button it will take me back to posts I've already read (sometimes several pages back). I do read the forum on a couple of PCs as well as the phone, but haven't noticed whether it's a syncing issue between these and the phone or just the phone if you kwim.
Has anyone had anything similar?