Leaverbuster hit-and-run punishment, no rhyme or reason

A few weeks/month ago, I posted a bug report about Leaverbuster showing an inaccurate leaver message, and wanting me to type "I agree". I also reported the bug where it punished me for no reason, AND I finally reported the bug where it KEPT punishing me after the leaverbuster countdown was finished.

The problem disappeared, so I figured RIOT fixed it.

But today I logged into my account after 11 days of playing on Latin America North, and when I joined a queue with a friend, I got punished out of nowhere. No warning, no dialog telling me I've been leaving, no countdown, nothing. And it only punished me for 1 game. It immediately stopped after my first game. Not only that, but I looked at my match history, and, of course, I haven't left any games, so it's not only random but really really inaccurate.

See the screenshot.