I just got 19.8.5 and the bass still disappears, not the speaker loss that this topic is about, that hasn't happened since I did the full car reset when it slept overnight. That initial issue hasn't returned, but everyone else on this thread seems to be speaking of the bass dropping out that I also mistook for the titular issue on my LA trip. The Tech told me he was getting a LOT of reports of this and the Engineers thought it was SW vs HW. Sadly it wasn't a SW fix that made it into the latest release, but I do love watching the car drive me places these days.
-Randy