Thanks for the suggestion. Unfortunately after 6 un-pairing / re-pairings, the results are the same.

I have tried re-pairing while a2dp and enabled and a2dp was disabled.

I have triple checked the Bluetooth address.

As an experiment, I paired (and then un-paired) the headset with a Mac and achieved full a2dp support including controlling iTunes with the headset controls, so I know the headset works correctly.

Any other suggestions?