Best answer by Rhythmicity
People in that thread are reporting that reposts, "un-reposts", follows, unfollows and likes aren't working properly right now. SC has admitted a problem with reposts but has not confirmed the other issues despite many reports. You might want to monitor that thread or chime in if you feel you are having the same problem.
Personally I have found that if I follow an artist right now, often the follow won't "stick"; in other words if I reload the page after I follow someone, I find that I never actually followed them.
We've confirmed in that other thread that un-reposts are affected just as bad as reposts, which is what leads me to believe that un-follows are affected just as bad as follows.
You unfollow them, but your action doesn't "stick", so behind the scenes as far as SC is concerned, you never unfollowed them. Therefore their music, etc., still shows up in your stream.