It seems to keep changing which 64 sites are on. I think this has happened a couple of times. I am absolutely certain it has happened at least once - i set certain sites as part of my ‘on’ sites and switched others to ‘off’ and have some back later and the selection has been different. It’s quite frustrating as it led me to miss an article about an event that I would have liked to go to.
I have the same issue, I select the 64 sites, I hit on save this sites, but if I immediately hit again to choose them I see that no change has been made and newsblur chooses the sites with a popularity criteria.