I use Spotify over wireless Android Auto in my 22 350h and pretty much every drive I take, even if it's just 20 minutes, my music will cut out at least once at some point in the drive (many times on longer drives). AA seems to stay connected the whole time (maps continues updating on the screen), but the music goes silent even though Spotify appears to continue playing. To get the sound back I have to cycle through the car's audio sources (FM/AM/Amazon/XM) and when I get back to AA the audio will return. I'm happy to buy a new phone if I'm the only one with this issue and a new phone will fix it.

 

Try post your question in NX 2nd Gen. Maybe someone over had the same issue as you.
Sound like an AA audio out issue with the car software. There are 2 audio channel output in your Car. Primary is your phone calls and maps. When your playing music and google map/waze play a direction audio it will override your music channel. Usually when that happen it will auto return to your music channel. In this case it didn't return, you manual change the audio sources to trigger back the music channel.

 

Nothing to do with returning to AA audio source.
There is something with Android Auto integration.
Apple car play doesn't have this issue it seems.
if you search online, there are many Toyoto owners with the same issue.