While my Samsung Galaxy S4 is connected to my JVC KD-AHD71BT headunit with bluetooth, Waze pauses the music when Waze wants to say an alert or guidance, but you will not hear anything (other than silence) or you will only hear the last word or two of the sentence before the music resumes. I used the default Samsung S4 / Android music app, but I also tried Rocket Player and the bug happens with both.
If I don't have music playing at all with the JVC set to the bluetooth input, sometimes I will still not hear any guidance/prompts (or it cuts off) from Waze until I click "Close All" to close all other apps on my Galaxy S4 (because the music app may still be loaded in memory but paused).
Android version 4.3
Build number JSS15J.1545VRUEMK2
When I use the same phone in a different car with the Belkin CarAudio Connect bluetooth (the Beklin connects to the Aux input of the car), the problem does not occur.
Also, once in a while, regardless of which bluetooth/car I use, sometimes the music audio will pause and get stuck in the pause state, and then I have to go to the music player and click on play again.