Using MQTT Broker that is subscribed to
$aws/things/chicken-door/shadow/name/door/#
what does it get when you publish and empty message to
$aws/things/chicken-door/shadow/name/door/get
I'm wondering now if the returned MQTT message is to big for the default 256/128 byte pubsub buffer size.
You could try increasing the buffer size with setBufferSize() to something larger, the size would depend on how large the /get reply is.