Update for those using Waze in AA, about the issue causing music to fade up and down over and over. The bug has been already reported to Waze developers and they are already working on it.
Meanwhile, I found this interesting post on AA forum:
"The bug is a perpetual overlay Waze notification of distance remaining and upcoming turn on your phone despite running AA. You'll see it if you swipe to unlock the phone. It is the same notification you will see on AA away from Waze screen or as card on AA home screen. This is likely causing the audio to attenuate on/off.
For now, press and hold on the notification to bring up the notification details, toggle Waze Android Auto Notification off and back on. This rids the overlay notification on the phone without disabling Waze notification on AA. You will only have to do this once. This can also be accessed from phone settings>Apps>Waze>Notification>Waze Android Auto Notification> toggle off and back on."