A curious problem arises when I add a third user in version 2.9.1. Once a third user is added I can no longer post under Admin even though Admin is logged in and the full dashboard is available. The post author menu at the bottom of the edit page doesn't even contain Admin as a choice. It's ok for Admin and one other user but not when a second additional user is added. I have only tried this when the other users are authors and not for other user categories. What's going on here?