Your comments

Hi, I've done as you suggested.

I can confirm that I've successfully made Xiaa the default player. This has prevented playback start from the default Android music player, when switching the car radio back to BT.

I have still issues with lack of sound through BT. In the next days I will experiment some more with this issue. The car radio seems to send BT "pause", not stop, as this is what the radio shows in the display. However, when the radio says "pause", Xiaa stops playing.

I will keep you updated.