`StopFromStage` not delivered

I am using `DrainingControl` to toggle my kafka subscribe state. ```java public pause() { this.drainingControl .drainAndShutdown(system.executionContext()) ..... } public start() { this.drainingControl = this.kafkaGraph.run(this.system); } ``` when I call the `pause()` method, the actor system complains `StopFromStage` wasn't delivered to kafka-consumer-actor...