Audio volume randomly lowers in car/truck while iPhone is connected wireless to CarPlay

Audio volume randomly lowers in car/truck while iPhone is connected wireless to CarPlay. This occurs when playing FM radio and music apps such as Spotify. It acts as if a notification is coming in from the iPhone but there are no visual notifications on the iPhone to confirm that's the cause.

I did find 2 work arounds but still believe there is a bug in CarPlay - either on the Apple side, the GM side or both.

Workaround #1 - If I set the physical switch on the side of my phone to mute/ring/silent button on (muted) then the problem goes away. So far it seems I still get visual and audible notifications through CarPlay in the vehicle. However, it is a pain is to remember to turn mute off (audio notifications on) when you get out of the car.

Workaround #2 - In the vehicle, under the CarPlay settings (while your iPhone is connected) there is a "WHEN CONNECTED TO CARPLAY" "Silent Mode" setting where mine was set to "mirror iPhone". After setting it to "Turn On Silent Mode" the problem seems to have stopped. I haven't noticed any side effects from doing this yet although I do get a red indication every now and then on the vehicle screen and sometimes on the iPhone that I believe is telling me my iPhone is muted.

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And when I say this happens randomly.... I have done everything I could to reproduce it on demand and have not. My only hunch is it is related to the vehicle RPMs. Maybe GM-Car/Truck software is telling the CarPlay software something when RPMs are between a certain range (possibly because engine noise?) and then that causes (incorrectly) the CarPlay software to turn the volume down. Just a guess at this point. I would be very interested in debugging this with the engineers who could fix it.