After staff logs in, the 'members online now' displays that the member has logged in, but does not show the member under staff online. The profile page does show that the staff member is online.
Only after a bit the staff member becomes visible on 'staff online'.
Thats weird. It happened just now on a clean install with newly imported DB. Maybe there is a cache issue going on, as this was the first login for that staff member. In which case the bug is so exotic that its beyond trivial.