LocalTaskService don't remove the listeners that are created in:

  public void registerForEvent(EventKey key, boolean remove, EventResponseHandler responseHandler) {
    SimpleEventTransport transport =
        new SimpleEventTransport(taskServiceSession, responseHandler, remove);
    taskServiceSession.getService().getEventKeys().register(key, transport);
  }


Notice that a client of this method can't remove it later, becouse the method return void.


This method is called by SyncWSHumanTaskHandler.connect()


 private void registerTaskEvents() {
 TaskCompletedHandler eventResponseHandler = new TaskCompletedHandler();
        TaskEventKey key = new TaskEventKey(TaskCompletedEvent.class, -1);
        client.registerForEvent(key, false, eventResponseHandler);
        key = new TaskEventKey(TaskFailedEvent.class, -1);
        client.registerForEvent(key, false, eventResponseHandler);
        key = new TaskEventKey(TaskSkippedEvent.class, -1);
        client.registerForEvent(key, false, eventResponseHandler);
    }
 

See that the listeners aren't save to remove later. If don't remove the listeners, they are invoked later.

PS: This can generate "Illegal method call. This session was previously disposed" - when a task is to be completed.