Created attachment 122981 [details]
Patch to fix the issue

SW: Pulseaudio 8.0 / BlueZ 5.39

Symptoms:
While disconnecting/reconnecting a paired bluetooth headset (LG HBS750) audio fails roughly on every other connection.

On a failed connection "pactl list cards" shows the bluetooth device's card but "Active Profile: off". Issuing "pacmd set-card-profile X a2dp_sink" makes audio work immediately.

I realized that when this happened, the previous disconnection did not remove the card, instead it was only configured for "Active Profile: off" but otherwise left in place.

Upon looking at PA debug logs I saw that the transport for the a2dp_sink was first set into disconnected state and then into idle state. In "device_connection_changed_cb()" this causes the "pa_bluetooth_device_any_transport_connected()" return true and the module-bluez5-device is not unloaded.

Further investigation shows that this is caused by a race of module-bluez5-device.c:thread_func() and MediaPoint1::ClearConfiguration():

When the FD in thread_func() is closed (POLLHUP) an BLUETOOTH_MESSAGE_STREAM_FD_HUP message is sent into the main thread. The handler of this message unconditionally sets the transport into IDLE state. This is a problem if it has already been set into DISCONNECTED state.

See attached patch for a fix.