Accumulation causes node propagation failure which results in rule firing when it is not supposed to. Please see attached code file to reproduce the issue. Rule "RS7402.42.2" is supposed to fire once but it manages to fire twice without getting deactivate.

2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - ACTIVATION CREATED rule:RS7365.4.6_ activationId:RS7365.4.6_ [1, 2, 3, 4, 12] declarations: $benefitAssessmentResults=BenefitAssessmentResults
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - BEFORE ACTIVATION FIRED rule:RS7365.4.6_ activationId:RS7365.4.6_ [1, 2, 3, 4, 12] declarations: $benefitAssessmentResults=BenefitAssessmentResults
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - OBJECT ASSERTED value:EvaluatedData factId: 13
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - OBJECT MODIFIED value:BenefitAssessmentResults factId: 12
RS7365.4.6_ FIRED
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - AFTER ACTIVATION FIRED rule:RS7365.4.6_ activationId:RS7365.4.6_ [1, 2, 3, 4, 12] declarations: $benefitAssessmentResults=BenefitAssessmentResults
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - ACTIVATION CREATED rule:RS7402.42.2_ activationId:RS7402.42.2_ [1, 2, 3, 5, 11, 4, 12, 13, 15] declarations: $currentMortgagePaymentAmount=0.0; $evaluatedData=EvaluatedData; $sum_1=9180.0
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - ACTIVATION CREATED rule:RS7402.42.2_ activationId:RS7402.42.2_ [1, 2, 3, 5, 10, 4, 12, 13, 14] declarations: $currentMortgagePaymentAmount=0.0; $evaluatedData=EvaluatedData; $sum_1=9180.0
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - BEFORE ACTIVATION FIRED rule:RS7402.42.2_ activationId:RS7402.42.2_ [1, 2, 3, 5, 11, 4, 12, 13, 15] declarations: $currentMortgagePaymentAmount=0.0; $evaluatedData=EvaluatedData; $sum_1=9180.0
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - OBJECT MODIFIED value:EvaluatedData factId: 13
RS7402.42.2_ FIRED
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - AFTER ACTIVATION FIRED rule:RS7402.42.2_ activationId:RS7402.42.2_ [1, 2, 3, 5, 11, 4, 12, 13, 15] declarations: $currentMortgagePaymentAmount=9180.0; $evaluatedData=EvaluatedData; $sum_1=9180.0
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - BEFORE ACTIVATION FIRED rule:RS7402.42.2_ activationId:RS7402.42.2_ [1, 2, 3, 5, 10, 4, 12, 13, 14] declarations: $currentMortgagePaymentAmount=9180.0; $evaluatedData=EvaluatedData; $sum_1=9180.0
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - OBJECT MODIFIED value:EvaluatedData factId: 13
RS7402.42.2_ FIRED
2014-09-05 23:23:02 INFO WorkingMemoryConsoleLogger:51 - AFTER ACTIVATION FIRED rule:RS7402.42.2_ activationId:RS7402.42.2_ [1, 2, 3, 5, 10, 4, 12, 13, 14] declarations: $currentMortgagePaymentAmount=18360.0; $evaluatedData=EvaluatedData; $sum_1=9180.0