So far, what have "worked" for me is:
1) Refresh the Inbox (with F5 or clicking on the Inbox text) until the number of unread items (the white number in the red circle changes from 0 to any value).
2) Select and Unselect the "Unread Only" checkbox until the unread items appear on the screen.
3) Click on any item, open it in a new tab by clicking on the title, returning to the inbox with the "back to inbox" link and continue with next unread item
4) Once all unread items are reviewd, repeat the process !!!
Behaving itself so far this morning....
Let's keep our finger crossed