Does anyone know what this would be indicative of?  I’ve seen it occur periodically at which point I have to discard the session.  I flatten and assert my data, run the rules, and then retract the handles collected on assertion.  I’ve ensured the fact handle parameter is never null.  I have the stateful session wrapped in a synchronized business façade, so I don’t think it should be a concurrency issue (unless I have a bug of course).  I’m running Drools 5 M4.

java.lang.NullPointerException

        at org.drools.util.RightTupleIndexHashTable.remove(RightTupleIndexHashTable.java:224)

        at org.drools.reteoo.JoinNode.retractRightTuple(JoinNode.java:204)

        at org.drools.reteoo.ObjectTypeNode.retractObject(ObjectTypeNode.java:210)

        at org.drools.reteoo.EntryPointNode.retractObject(EntryPointNode.java:190)

        at org.drools.common.AbstractWorkingMemory.retract(AbstractWorkingMemory.java:1078)

        at org.drools.common.AbstractWorkingMemory.retract(AbstractWorkingMemory.java:1045)