Akka.Net Version: 1.3.9
Platform: Windows 10 - Microsoft Service Fabric

According to the docs:

Actors are automatically removed from the registry when they are terminated, or you can explicitly remove entries with DistributedPubSubMediator.Unsubscribe.

https://getakka.net/articles/clustering/distributed-publish-subscribe.html

But after terminating the subscriber actor, messages published to the subscribed topic keep being redirected to the subscriber's dead letters.
Demo: https://github.com/pedroyan/MediatorBug