I just updated to the 11.2 beta and the music issues are the worst I've ever experienced, It is to the point where it works for about 1-2 minutes and then disconnects. I've tried completely restarting the phone and a fresh pairing to the car with a new profile and still no improvement.
I drive a 2016 BMW M4, have a iPhone 7 plus and did not have problems with earlier releases of iOS. The word is its a problem with the car but that just doesn't make since, the only change has been iOS on the phone, seems obvious to me. Those not on the Beta program having issues, expect it to get worse.
I've been a long time apple customer and fan of the iPhone, i use the Apple Music service, however I use my phone and this service mostly to listed to music in the car. Given that this no longer works properly I may be moving away from apple and their services to other solutions like Android and Spotify, which seem to work without any trouble on every car I've used them with.