Android: Feeds not refreshing, "read" count wrong

For example, xkcd shows 1 unread message. If I open the feed, there are no unread. If I mark the feed as read, it is no longer displayed, correctly. But refreshing all feeds, it comes back with 1 unread. Opening the feed, they are still all read.

Deleting all app data fixed the problem, briefly. All feeds refreshed. But then the exact same behavior recurred.

app version: 4.1.0
android version: 5.0.1
device: LGE Nexus 5 (hammerhead)
memory: normal
speed: 24 in 99
premium: yes