I believe I found the reason for this, Z3 dual on MM too, annoying stutters when playing music too, using a Sony SBH20 Bluetooth headset. Changing music players didn't work, It seems to be static electricity, I'm not an expert but it only happens when in jeans(the material in those causes more static electricity when rubbed?) or when in other garments when you do sudden movements. Placing the device on a stationary surface has smooth playback, placing it in your pocket in jeans causes stutter almost as soon as you start walking, placing it in my shorts or holding the phone in my hand allow smooth playback even if I move around but will stutter once when I do sudden jerky movement.
It's obviously kind of an oversight, can't exactly blame Sony wholly, but still, Jeans are common. Guess we should try to experiment with stuff like a phone pouch to see if it works.