Comment 3 for bug 1838180

It sounds like the log messages relating to the issue are:

  Jul 27 22:54:49 hostname gsd-media-keys[2755]: Unable to get default sink
  ...
  Jul 27 22:55:04 hostname bluetoothd[1423]: Unable to get Headset Voice gateway SDP record: Device or resource busy
  Jul 27 22:55:04 hostname bluetoothd[1423]: connect error: Device or resource busy (16)

Which suggests it's the kernel that's behaving differently, via PulseAudio.

Please try some newer (or older) kernels from:

  https://kernel.ubuntu.com/~kernel-ppa/mainline/?C=N;O=D

and tell us which versions, if any, avoid the bug.