About that : it seems that all the feeds I saw broken are in fact read correctly, BUT the items are not in chronological order.
I don’t know if it’s the feeds themselves or newsblur, but I think that since it’s not “correct”, then the “unread” filter does not display the new posts correctly. At least, it seems like it.
For the gamekult feed, there is an item whose date is something in “2016”. Maybe that’s the cause as well.
Hope that will help;