Thanks for letting them pile up. I found the cause. Your unread records were correct, but in All stories with Newest first, NewsBlur was checking unread status against the wrong page of the unread list. So older unread stories could appear in the folder but be treated as read, which made next unread skip them.
I have a fix ready. I’m deploying it now and you should be able to keep using All stories and Newest first without those unread articles getting stuck.