2nd time I’ve seen this. A red notification appears at the hamburger, when I hover on it, it indicates “total flagged posts”, when I click on it it takes me to /admin/flags/active, but there aren’t any active flags.
When I click on the hamburger I then see that there is a post that needs approval, and when I click on that, then it takes me to /queued-posts, where there is indeed a queued post awaiting approval.