Unread only view: the latest unread mail is displayed twice

If go into inbox (8.0.2)and select view unread onlyand then click on the date column to sort (latest at the top) the latest unread mail is displayed twice at the top - but also at the bottom. Another unread mail (1) disappears.

Any ideas on why this latest email is displayed twice. If some one sends me a new mail - the previously displayed twice is now displayed once and the new one is at the top and bottom.

This only occurs when sorting by date. I have tried replacing design, and locally deleting bookmark, cache etc but to no avail.

Any one got any ideas?

Thanks in advance

Monika