Unhandled messages from subscription actor

We are using the EventStore JVM client, and are subscribing to a category stream using the StreamSubscriptionActor. Once in a while, maybe once a month, the actor seems to enter a state where all events fail to get handled, causing our handler for Akka UnhandledMessages to get a message for each event supposed to be handled by the StreamSubscriptionActor. It looks like our application still gets all the events, maybe because we have gotten a new instance of the subscription actor or something like that? A restart of the application fixes the problem.

The unhandled message is of type StreamEventAppeared(IndexedEvent(ResolvedEvent(EventRecord(…))))

Has anyone encountered similar problems before, or have any idea what may be causing it, and how it can be avoided?