Currently, call from AS to CC to spawn new instances is synchronous. It has a timeout. Hence, there can be a situation like below,
Call from AS to CC to spawn new instance can time out.
Due to that, AS will not add the pending member for that call.
But CC's attempt to spawn the instance can become successful with a very high delay (> time out)
Meanwhile, the agent can send the instance activated event, even before CC sends the member started event. Since this member is not there in the topology, the event will get discarded. Hence, the member will never get activated in topology, and remains in created state. This is an additional member!