There is some suspicion that one of the issues at play in the subscribing issue is a visual/front-end problem. The already-subscribed user is presented with a

There is some suspicion that one of the issues at play in the subscribing issue is a visual/front-end problem. The already-subscribed user is presented with a "subscribe" button instead of "unsubscribe". They think they aren't subscribed, click the button, which then actually unsubscibes the user.