My new Z2 D6503 is on .167 (4.4.4 KK) firmware, and when I connect it to my car's bluetooth audio system, sometimes it stutter really bad that I cannot enjoy the music. My car is 2014 and it also has the ability to read text messages.
So after some investigation, I found a tempoaray solution to the dropouts:
1) If I just disable throw and reconnect, stuttering still exist.
2) If I just disable BT and re-enable, sometimes it fixes it but sometimes I lose AVRCP (control via car)
3) going into bluetooth setting, and diable MAP (text message), dropouts improved dramatically (from every 10 secs to every 1 mins or so)
4) disabling bluetooth Phone audio (so the only thing left is Bluetooth media audio) completely solves the dropout.
Sony should consider using a different bluetooth stack
