Events not firing in Listeners in multi-thread environment

Issue

When you start 5 threads that call createNotification, thereby firing 5 CreateEvents, only the first event is sent to the createNotification method in ListenerImpl.

The other 4 events are, as far as we can see, silently dropped.

Is this correct behaviour? We expected the other 4 events to be queued internally by JBoss and handled sequentially by ListenerImpl.

@Stateless
public class Notifier {
    @Inject
    Event<AppointmentCreatedEvent> aftaleCreatedListeners;

    public void createNotification(Appointment data) {
        aftaleCreatedListeners.fire(new CreateEvents(data));
    }
 }

public interface Listener {
    @Asynchronous
    public void createNotification(@Observes(during = TransactionPhase.AFTER_SUCCESS) Appointment event);
}

@Singleton
public class ListenerImpl implements Listener {
    private static Logger logger = CapLog.getCategory(ListenerImpl.class);

    @Override
    @Asynchronous
    public void createNotification(@Observes(during = TransactionPhase.AFTER_SUCCESS) Appointment event) {
       logger.debug("ListenerImpl Event triggered, Oid=" + event.getNew().getAppointmentId().serialize());
        try {
                Thread.sleep(60*1000);
        } catch (Exception e) {        
       }
    }
}

In order to ensure that all 5 events are handled, we have added the following annotation to the createNotification method in ListenerImpl: @Lock(LockType.READ)