I’ve noticed recently that when viewing a folder in the iOS app, if I tap the Mark All As Read checkbox at the top of the article list for that folder, while the articles do disappear from that column, the unread article count for the folder in the leftmost column does not get reset to zero. For example it will claim there are 2 unread articles, but none are shown in the second column. I usually have to refresh the folder list to get it to update the article count.
Previous versions would update this count when tapping Mark All As Read.