My wife (username ‘lyriendel’) subscribes to my Blurblog. When set to “Unread Only”, certain already read stories always appear in that feed for her, even though the app knows they are read (showing them not in bold). The same stories appear, out of chronological order, in both “Newest First” and “Oldest First” views. This occurs on both the desktop and iOS apps.
The stories marked as “read” in these screenshots were read by her long ago, but are still appearing in the feed many days later.
Another problem may or may not be related. in her iOS app, the number of articles that are shown when the settings are “Unread Only / Oldest First” gets mismatched with the actual unread count, shrinking over many days until in the extreme case recently there were 238 unread articles and none showing up in that mode. This was fixable only by uninstalling and re-installing the app. Screenshots: