Ah, so the issue is that an actor both replies with an error message, and publishes one. One possible solution is to say that only one actor should “own" the error. If actor_a asked actor_b to do something, and an error occurs, then actor_a is the one responsible for handling/reporting it. You can do this by changing the error handling case to only publish the error message if their was no return address attached to the original request message. Thus you Reply OR Notify, rather than Reply AND Notify, and there is only one error message.