Detect bluetooth SPP disconnection without using packets

I have some Bluetooth devices which connect to an Android phone, however I'm having trouble detecting disconnections. The bluetooth devices don't send data packets unless they need to, so it's not an option to use a watchdog on packet reception to detect a disconnect. I've read that you can use the ACLDisconnected broadcast, but this event is never firing for me (I've waited minutes). What is a reliable way to detect a disconnection in Android 6?

Here is my AclDisconnect registering code:

_filter = new IntentFilter();
_filter.AddAction(BluetoothDevice.ActionFound);
_filter.AddAction(BluetoothDevice.ActionBondStateChanged);
_filter.AddAction(BluetoothAdapter.ActionDiscoveryStarted);
_filter.AddAction(BluetoothDevice.ActionAclDisconnected);
_filter.AddAction(BluetoothDevice.ActionAclDisconnectRequested);
context.RegisterReceiver(_bluetoothDeviceReceiver, _filter);

And the callback (which doesn't fire on disconnect)

public override void OnReceive(Context context, Intent intent)
{
    string action = intent.Action;

    if (action == BluetoothDevice.ActionAclDisconnected || action == BluetoothDevice.ActionAclDisconnectRequested)
    {
         Interlocked.CompareExchange(ref Disconnected, null, null)?.Invoke();
    }
 }