droid turbo and car bluetooth sound (bmw / subaru)

I am looking for any suggestions for BT connectivity between Turbo and my car. From day 1 when the phone was on KK the sound of the remote party was coming out garbled. I managed to find a sequence of steps to clear it up on a one time basis (unpair/re-pair in specific order), but even since upgrading to LL nothing helps.
It seems I am not the only one with such issue:
https://www.youtube.com/watch?v=A8C1jyao89o

any files/profiles to edit? any hidden settings i can play with? I have not found anything in Play or Xposed