It's that encryption thing. I saw recently a comment in the Amber update about a fix for errors when signing multiple events at once. I think this is maybe what it fixed. Just have to test it again.
A "report" also generates a "mute" because you probably want to mute the spammer or whatever. That part is logical. The signing of both events breaks/broke it, though.
Publishing a new, singular "mute" event from a client that isn't locked up straightens it out again. I could break it and fix it at will this way.
Like I said...months. It seemed random at first. Devs are slammed with real shit, so I just started beating on it. They'll get to it if they didn't already. Vitor knows about it.