2014-06-06 13:18:43,594 WARN info.magnolia.event.SimpleEventBus : Exception caught when dispatching a class info.magnolia.task.event.TaskEvent event with class info.magnolia.module.workflow.jbpm.humantask.ProcessTaskEventHandler eventHandler.
org.jbpm.workflow.instance.WorkflowRuntimeException: [info.magnolia.workflow.Publication:1,402,053,349,513 - Publish:5] – null
at org.jbpm.workflow.instance.node.WorkItemNodeInstance.internalTrigger(WorkItemNodeInstance.java:135)
at org.jbpm.workflow.instance.impl.NodeInstanceImpl.trigger(NodeInstanceImpl.java:155)
at org.jbpm.workflow.instance.impl.NodeInstanceImpl.triggerNodeInstance(NodeInstanceImpl.java:337)
at org.jbpm.workflow.instance.impl.NodeInstanceImpl.triggerCompleted(NodeInstanceImpl.java:296)
at org.jbpm.workflow.instance.node.JoinInstance.triggerCompleted(JoinInstance.java:259)

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Caused by: java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
at java.util.HashMap$EntryIterator.next(HashMap.java:834)
at java.util.HashMap$EntryIterator.next(HashMap.java:832)
at java.util.HashMap.writeObject(HashMap.java:999)
at sun.reflect.GeneratedMethodAccessor621.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:950)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1482)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1413)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1159)