Intermittent exception in webservice callouts

Issue

Caused by: javax.xml.ws.WebServiceException: java.lang.NullPointerException
at org.jboss.ws.core.jaxws.client.ClientImpl.handleRemoteException(ClientImpl.java:310)
at org.jboss.ws.core.jaxws.client.ClientImpl.invoke(ClientImpl.java:243)
at org.jboss.ws.core.jaxws.client.ClientProxy.invoke(ClientProxy.java:171)
at org.jboss.ws.core.jaxws.client.ClientProxy.invoke(ClientProxy.java:157)
at $Proxy1054.process(Unknown Source)
at com.example.WSTransportSender.sendReceive(WSTransportSender.java:48)
... 30 more
Caused by: java.lang.NullPointerException
at org.jboss.ws.core.CommonSOAPBinding.getParameterFromMessage(CommonSOAPBinding.java:889)
at org.jboss.ws.core.CommonSOAPBinding.unbindResponseMessage(CommonSOAPBinding.java:613)
at org.jboss.ws.core.CommonClient.invoke(CommonClient.java:396)
at org.jboss.ws.core.jaxws.client.ClientImpl.invoke(ClientImpl.java:231)