Read articles reappear as unread

Whilst reading articles on my laptop using the web page in Firefox 50.1.0 on Windows 10 Build 14393.693, I actually read a couple of dozen articles, and marked “older stories read” several times. The articles all greyed out. When I finished the outstanding articles at 18:10, which included articles up to and including 18:00, I clicked back to the “All site stories” heading, and whilst the summary under my username at the top said 15, there were maybe 25 or 30. Odd, so I clicked it again- the same. So I refreshed the page, and now I have 44 articles back to 10:57 today, from virtually all of the different feeds that I subscribe to, and most of them I can specifically remember reading the headline and having been included in the “mark above as read”.
I’ve had this sort of thing before on Android, but cannot recall it on the web site.
18:58 Newsblur is now telling me that I have -6 articles to read! I had gone off to do something else and returned to NewsBlur. It was still showing 44 articles, so I looked through them and marked above as read. I clicked on All Site Stories, and got 19, 2 of which were actually new, though they all showed as new unread. So I marked All Above Read, and that showed me I had -6 left to read. Yet clicking on All Site Stories shows 15 unread stories in the right hand pane. Having typed the above and checked back to NewsBlur, I now have 42 unread stories. Surprise! They go back to 10:42 - even earlier.


Working fine today.