We are using drools-core-6.3.0.Final-redhat-5.jar.
The Rules are being executed in an embedded container in our application.
While executing the Rules in the container, for few scenarios we notice the following error.
These issues are not reproducible in unit test mode, while trying to simulate with the same fact data as available during application execution.
Sometimes the rule actually fires (I see the logs for the Then side of a rule), and we still observe this exception.

How can we track, if this is a specific rule which is throwing this exception everytime or some issue with the fact?
I am unable to pin it on the facts, since similar fact with slightly different data values works fine.

java.lang.NullPointerException
at org.drools.core.base.extractors.BaseDateClassFieldReader.getLongValue(BaseDateClassFieldReader.java:80)
at org.drools.core.base.extractors.BaseDateClassFieldReader.getHashCode(BaseDateClassFieldReader.java:111)
at org.drools.core.base.ClassFieldReader.getHashCode(ClassFieldReader.java:197)
at org.drools.core.rule.Declaration.getHashCode(Declaration.java:298)
at org.drools.core.util.AbstractHashTable$TripleCompositeIndex.hashCodeOf(AbstractHashTable.java:713)
at org.drools.core.util.index.LeftTupleIndexHashTable.getOrCreate(LeftTupleIndexHashTable.java:449)
at org.drools.core.util.index.LeftTupleIndexHashTable.add(LeftTupleIndexHashTable.java:379)
at org.drools.core.phreak.PhreakAccumulateNode.doLeftInserts(PhreakAccumulateNode.java:145)
at org.drools.core.phreak.PhreakAccumulateNode.doNode(PhreakAccumulateNode.java:95)
at org.drools.core.phreak.RuleNetworkEvaluator.switchOnDoBetaNode(RuleNetworkEvaluator.java:565)
at org.drools.core.phreak.RuleNetworkEvaluator.evalBetaNode(RuleNetworkEvaluator.java:536)
at org.drools.core.phreak.RuleNetworkEvaluator.evalNode(RuleNetworkEvaluator.java:372)
at org.drools.core.phreak.RuleNetworkEvaluator.innerEval(RuleNetworkEvaluator.java:332)
at org.drools.core.phreak.RuleNetworkEvaluator.outerEval(RuleNetworkEvaluator.java:166)
at org.drools.core.phreak.RuleNetworkEvaluator.evaluateNetwork(RuleNetworkEvaluator.java:123)
at org.drools.core.phreak.RuleExecutor.evaluateNetwork(RuleExecutor.java:65)
at org.drools.core.common.DefaultAgenda.evaluateEagerList(DefaultAgenda.java:1004)
at org.drools.core.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:961)
at org.drools.core.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1292)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.internalFireAllRules(StatefulKnowledgeSessionImpl.java:1294)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1281)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1260)
at com.highmark.eitmet.transformers.CorrelationEngineTransformer.triggerCorrelationBusinessRule(CorrelationEngineTransformer.java:113)
at com.highmark.eitmet.transformers.CorrelationEngineTransformer.transform(CorrelationEngineTransformer.java:60)
at com.highmark.gupfdr.federator.UniversalFederator.federate(UniversalFederator.java:31)
at com.highmark.gupfdr.ejb.FederationProcessBean.process(FederationProcessBean.java:189)
at com.ibm.websphere.scheduler.EJSRemoteCSLWRITETO_DB_FEDERATOR_bbf2322f.process(EJSRemoteCSLWRITETO_DB_FEDERATOR_bbf2322f.java)
at com.ibm.websphere.scheduler._TaskHandler_Stub.process(_TaskHandler_Stub.java:269)
at com.highmark.gupfdr.federator.FederatorThreadRunner.run(FederatorThreadRunner.java:36)
at com.ibm.ws.asynchbeans.J2EEContext$RunProxy.run(J2EEContext.java:270)
at java.security.AccessController.doPrivileged(AccessController.java:311)
at javax.security.auth.Subject.doAs(Subject.java:494)
at com.ibm.websphere.security.auth.WSSubject.doAs(WSSubject.java:133)
at com.ibm.websphere.security.auth.WSSubject.doAs(WSSubject.java:91)
at com.ibm.ws.asynchbeans.J2EEContext$DoAsProxy.run(J2EEContext.java:337)
at java.security.AccessController.doPrivileged(AccessController.java:341)
at com.ibm.ws.asynchbeans.J2EEContext.run(J2EEContext.java:805)
at com.ibm.ws.asynchbeans.WorkWithExecutionContextImpl.go(WorkWithExecutionContextImpl.java:222)
at com.ibm.ws.asynchbeans.ABWorkItemImpl.run(ABWorkItemImpl.java:206)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1881)

or :

java.lang.NullPointerException
at org.drools.core.base.ClassFieldReader.getHashCode(ClassFieldReader.java:197)
at org.drools.core.rule.Declaration.getHashCode(Declaration.java:298)
at org.drools.core.util.AbstractHashTable$TripleCompositeIndex.hashCodeOf(AbstractHashTable.java:713)
at org.drools.core.util.index.LeftTupleIndexHashTable.getOrCreate(LeftTupleIndexHashTable.java:449)
at org.drools.core.util.index.LeftTupleIndexHashTable.add(LeftTupleIndexHashTable.java:379)
at org.drools.core.phreak.PhreakAccumulateNode.doLeftInserts(PhreakAccumulateNode.java:145)
at org.drools.core.phreak.PhreakAccumulateNode.doNode(PhreakAccumulateNode.java:95)
at org.drools.core.phreak.RuleNetworkEvaluator.switchOnDoBetaNode(RuleNetworkEvaluator.java:565)
at org.drools.core.phreak.RuleNetworkEvaluator.evalBetaNode(RuleNetworkEvaluator.java:536)
at org.drools.core.phreak.RuleNetworkEvaluator.evalNode(RuleNetworkEvaluator.java:372)
at org.drools.core.phreak.RuleNetworkEvaluator.innerEval(RuleNetworkEvaluator.java:332)
at org.drools.core.phreak.RuleNetworkEvaluator.outerEval(RuleNetworkEvaluator.java:166)
at org.drools.core.phreak.RuleNetworkEvaluator.evaluateNetwork(RuleNetworkEvaluator.java:123)
at org.drools.core.phreak.RuleExecutor.evaluateNetwork(RuleExecutor.java:65)
at org.drools.core.common.DefaultAgenda.evaluateEagerList(DefaultAgenda.java:1004)
at org.drools.core.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:961)
at org.drools.core.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1292)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.internalFireAllRules(StatefulKnowledgeSessionImpl.java:1294)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1281)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1260)
at com.highmark.eitmet.transformers.CorrelationEngineTransformer.triggerCorrelationBusinessRule(CorrelationEngineTransformer.java:113)
at com.highmark.eitmet.transformers.CorrelationEngineTransformer.transform(CorrelationEngineTransformer.java:60)
at com.highmark.gupfdr.federator.UniversalFederator.federate(UniversalFederator.java:31)
at com.highmark.gupfdr.ejb.FederationProcessBean.process(FederationProcessBean.java:189)
at com.ibm.websphere.scheduler.EJSRemoteCSLWRITETO_DB_FEDERATOR_bbf2322f.process(EJSRemoteCSLWRITETO_DB_FEDERATOR_bbf2322f.java)
at com.ibm.websphere.scheduler._TaskHandler_Stub.process(_TaskHandler_Stub.java:269)
at com.highmark.gupfdr.federator.FederatorThreadRunner.run(FederatorThreadRunner.java:36)
at com.ibm.ws.asynchbeans.J2EEContext$RunProxy.run(J2EEContext.java:270)
at java.security.AccessController.doPrivileged(AccessController.java:311)
at javax.security.auth.Subject.doAs(Subject.java:494)
at com.ibm.websphere.security.auth.WSSubject.doAs(WSSubject.java:133)
at com.ibm.websphere.security.auth.WSSubject.doAs(WSSubject.java:91)
at com.ibm.ws.asynchbeans.J2EEContext$DoAsProxy.run(J2EEContext.java:337)
at java.security.AccessController.doPrivileged(AccessController.java:341)
at com.ibm.ws.asynchbeans.J2EEContext.run(J2EEContext.java:805)
at com.ibm.ws.asynchbeans.WorkWithExecutionContextImpl.go(WorkWithExecutionContextImpl.java:222)
at com.ibm.ws.asynchbeans.ABWorkItemImpl.run(ABWorkItemImpl.java:206)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1881)