How to start new process instance from custom WorkItemHandler in JBoss BPM Suite 6 ?

Issue

In custom workItemHandler we are using below code to start new process instance, but it fails with exception:

//execute method:   
long processInstanceId = workItem.getProcessInstanceId();
ProcessInstance ins = kSession.getProcessInstance(processInstanceId);
String processId = ins.getProcessId();      
ProcessInstance procInstance = kSession.startProcess(processId, null);
long newProcessInstanceId = procInstance.getId();

Exception:

. . .
Caused by: java.lang.IllegalStateException: KieSession with id 12 is already used by another context
    at org.jbpm.runtime.manager.impl.PerProcessInstanceRuntimeManager.validate(PerProcessInstanceRuntimeManager.java:165) [jbpm-runtime-manager-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
    at org.jbpm.persistence.processinstance.JPAProcessInstanceManager.getProcessInstance(JPAProcessInstanceManager.java:92) [jbpm-persistence-jpa-6.2.0.Final-redhat-4.jar:6.2.0.Final-redhat-4]
. . .