I don't know if you're still looking for an answer to this but it's happening because Google assistant is seizing the microphone as soon as you start route guidance. This forces the Ai Box to route audio as though it were a (mono) phone call rather than (stereo) media. The fix is to go in to Maps settings --> navigation settings --> Google assistant settings --> general --> hey/ok Google detection and toggle off for "while driving"I'm on the latest firmware (10/21), and while it has resolved the volume/audio channel issue for me on my Hyundai, the audio quality still drops out anytime Google Maps or an audio assistance is running.
Is there any way to force an override so all apps use the same higher quality audio channel?
According to the blurb this also toggle also affects other mapping apps that use ok Google detection eg Android auto