Read story randomly pops up as unread on the front page but not on "all site stories" page

Hi, I keep having this problem:

One particular story every few weeks shows up as unread in the “all site stories” box on the Newblur front page (https://newsblur.com/). But when I select “all site stories” from the sidebar, it doesn’t show up there and when I return to the front page, it’s gone from the front page too.

My memory might fail me, but I think this problem has kept happening even across different computers and browsers. I’ve also tried clicking the story when it shows up but hasn’t been enough to stop it from appearing again eventually.

Any idea what to do here? (My Newblur username is “aapo”.)