org.drools.runtime.rule.ConsequenceException caused by java.util.ConcurrentModificationException

We got the rule consequence exception which is caused by ConcurrentModificationException. This happened when we import the payments for the consumers in the batch, and one of the consumer failed. The rule is defined in the decision table in Guvnor. The source for the rule is attached. It's just a simple eligibility check.

Please investigate the issue. Thanks.

org.drools.runtime.rule.ConsequenceException: [Error: drools.insert(fact0 ): null]
[Near :

]
^
[Line: 1, Column: 0]
at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:23)
at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:943)
at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:885)
at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1086)
at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:660)

--------------------------------------------------------------------------------------------------------------------------------------------------------------------

[Line: 1, Column: 0]
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:374)
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.optimizeAccessor(ReflectiveAccessorOptimizer.java:138)
at org.mvel2.optimizers.dynamic.DynamicOptimizer.optimizeAccessor(DynamicOptimizer.java:62)
at org.mvel2.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:133)
at org.mvel2.MVELRuntime.execute(MVELRuntime.java:85)
at org.mvel2.compiler.CompiledExpression.getValue(CompiledExpression.java:104)
at org.mvel2.MVEL.executeExpression(MVEL.java:978)
at org.drools.base.mvel.MVELConsequence.evaluate(MVELConsequence.java:87)
at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:934)
... 52 more
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:931)
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:316)
... 60 more
Caused by: java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
at java.util.HashMap$ValueIterator.next(HashMap.java:822)
at org.drools.reteoo.EntryPointNode.updateSink(EntryPointNode.java:285)
at org.drools.reteoo.ObjectTypeNode.attach(ObjectTypeNode.java:279)
at org.drools.reteoo.builder.PatternBuilder.attachObjectTypeNode(PatternBuilder.java:234)
at org.drools.reteoo.ClassObjectTypeConf.<init>(ClassObjectTypeConf.java:93)
at org.drools.common.ObjectTypeConfigurationRegistry.getObjectTypeConf(ObjectTypeConfigurationRegistry.java:58)
at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:849)
at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:114)
at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:108)