Headset profile no audio; works with a2dp

Bluez version: 5.40
Pulseaudio: 6.0

I have headset that I am able to pair, connect, and play audio via the a2dp_sink profile of pulseaudio. When I switch to headset_head_unit profile, I can no longer send audio to the headset. I first went to pulseaudio to see if they had any suggestions as I found a very similar case to mine (https://bugs.freedesktop.org/show_bug.cgi?id=97064). 

Tanu kindly pointed out that there seemed to be missing a dbus signal from bluetoothd, specifically "PropertiesChanged" signal on MediaTransport1 interface. I did some inspection, and transport_update_playing() in profiles/audio/transport.c shows Playing = 0 and not 1, which is the case when using a2dp_sink profile.

Headset_head_unit:
bluetoothd[756]: profiles/audio/transport.c:transport_update_playing() /org/bluez/hci0/dev_00_11_C2_08_15_F6/fd0 State=TRANSPORT_STATE_IDLE Playing=0

a2dp_sink:
bluetoothd[756]: profiles/audio/transport.c:transport_update_playing() /org/bluez/hci0/dev_00_11_C2_08_15_F6/fd0 State=TRANSPORT_STATE_ACTIVE Playing=1

Any recommendation on what might be the issue? Happy to provide any logs that could be useful.