Your shun info is not really in database, it probably happened because it was not removed from memory. It's most likely caused by anti-mute evade that works slightly different..
I've updated the mute system to solve the problem and changed the mute time to be more informative. I believe your problem is already solved since i restarted the server, but i'll leave this topic opened in case you have anything to say. You may open new topic in Bug Report section if it happens again in the future, dont post them in General Discussion.