Getting "Operation failed with status CANCELLED" and "Endpoint is not open" errors when running clustered EJB client

Issue

I have done EJB clustering following solution article: How to make EJB's Clustered in JBoss EAP 6?.
I setup multiple remote connections configured as remote.connections=one,two,three,four......

The cluster EJB client works as expected but I get intermittent errors on exiting the client, they are printed in INFO logging level. For example:

2015-01-20 17:07:38 [RemotingConnectionClusterNodeManager.java] INFO  Could not create a connection for cluster node ClusterNode{clusterName='ejb', nodeName='cluster-nodex', clientMappings=[ClientMapping{sourceNetworkAddress=/0:0:0:0:0:0:0:0, sourceNetworkMaskBits=0, destinationAddress='xx.xx.xx.xx', destinationPort=4447}], resolvedDestination=[Destination address=xx.xx.xx.xx, destination port=4447]} in cluster ejb
java.lang.RuntimeException: Operation failed with status CANCELLED
    at org.jboss.ejb.client.remoting.IoFutureHelper.get(IoFutureHelper.java:93)
    at org.jboss.ejb.client.remoting.ConnectionPool.getConnection(ConnectionPool.java:77)
    at org.jboss.ejb.client.remoting.RemotingConnectionManager.getConnection(RemotingConnectionManager.java:51)
    at org.jboss.ejb.client.remoting.RemotingConnectionClusterNodeManager.getEJBReceiver(RemotingConnectionClusterNodeManager.java:77)
    at org.jboss.ejb.client.ClusterContext$EJBReceiverAssociationTask.call(ClusterContext.java:406)
    at org.jboss.ejb.client.ClusterContext$EJBReceiverAssociationTask.call(ClusterContext.java:380)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
2015-01-20 17:07:38 [RemotingConnectionClusterNodeManager.java] INFO  Could not create a connection for cluster node ClusterNode{clusterName='ejb', nodeName='cluster-nodey', clientMappings=[ClientMapping{sourceNetworkAddress=/0:0:0:0:0:0:0:0, sourceNetworkMaskBits=0, destinationAddress='yy.yy.yy.yy', destinationPort=4447}], resolvedDestination=[Destination address=yy.yy.yy.yy, destination port=4447]} in cluster ejb
org.jboss.remoting3.NotOpenException: Endpoint is not open
    at org.jboss.remoting3.EndpointImpl.resourceUntick(EndpointImpl.java:182)
    at org.jboss.remoting3.EndpointImpl.doConnect(EndpointImpl.java:261)
    at org.jboss.remoting3.EndpointImpl.connect(EndpointImpl.java:386)
    at org.jboss.ejb.client.remoting.NetworkUtil.connect(NetworkUtil.java:151)
    at org.jboss.ejb.client.remoting.NetworkUtil.connect(NetworkUtil.java:132)
    at org.jboss.ejb.client.remoting.ConnectionPool.getConnection(ConnectionPool.java:75)
    at org.jboss.ejb.client.remoting.RemotingConnectionManager.getConnection(RemotingConnectionManager.java:51)
    at org.jboss.ejb.client.remoting.RemotingConnectionClusterNodeManager.getEJBReceiver(RemotingConnectionClusterNodeManager.java:77)
    at org.jboss.ejb.client.ClusterContext$EJBReceiverAssociationTask.call(ClusterContext.java:406)
    at org.jboss.ejb.client.ClusterContext$EJBReceiverAssociationTask.call(ClusterContext.java:380)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)