this happened to me on the exact day i was driving home after the infotainment upgrade.
periodically this occurs again; super annoying. anytime Im slowing down at a light its a loud cheering like sound, and the reverse sound as well.
I've had it brought into service like 5x, and they always say they cant reproduce it... and waste my time. Even though I've given many videos and timestamps.
2016MX P90DL AP1.