Rules combined with OR and AND clauses and PROBABLY global variables throw a ClassCastException.
This issue is raised due to the discussion in user-list
http://drools.46999.n3.nabble.com/ClassCastException-after-migrating-from-Drools-4-x-to-v5-5-td4022292.html

I attached an isolated test.

This is the error that I get:

Caused by: org.drools.RuntimeDroolsException: com.test.drools.Rule_employeeContributionStartDateAfterAccountStartDate_ff664e4a040442f190ea42829e28cdd1Eval1Invoker@d3924bb
c : java.lang.ClassCastException: com.test.drools.EmployeeDetailsRulesModel cannot be cast to com.test.drools.Account
at org.drools.rule.EvalCondition.isAllowed(EvalCondition.java:119)
at org.drools.reteoo.EvalConditionNode.assertLeftTuple(EvalConditionNode.java:176)
at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:196)
at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:71)
at org.drools.reteoo.JoinNode.propagateFromRight(JoinNode.java:159)
at org.drools.reteoo.JoinNode.assertObject(JoinNode.java:148)
at org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:497)
at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:382)
at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:235)
at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:240)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:350)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:311)
at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:903)
at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:192)
at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:186)
at com.test.drools.Rule_employeePreloadSystemConstants_fa8d3c7c3b23439db5734ab24bd05240.defaultConsequence(Rule_employeePreloadSystemConstants_fa8d3c7c3b23439db57
34ab24bd05240.java:7)
at com.test.drools.Rule_employeePreloadSystemConstants_fa8d3c7c3b23439db5734ab24bd05240DefaultConsequenceInvokerGenerated.evaluate(Unknown Source)
at com.test.drools.Rule_employeePreloadSystemConstants_fa8d3c7c3b23439db5734ab24bd05240DefaultConsequenceInvoker.evaluate(Unknown Source)
at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1287)
... 37 more
Caused by: java.lang.ClassCastException: com.test.drools.EmployeeDetailsRulesModel cannot be cast to com.test.drools.Account
at org.drools.base.com.test.drools.Account1369078346$getAccountStartDate.getValue(Unknown Source)
at org.drools.base.ClassFieldReader.getValue(ClassFieldReader.java:87)
at org.drools.rule.Declaration.getValue(Declaration.java:233)
at com.test.drools.Rule_employeeContributionStartDateAfterAccountStartDate_ff664e4a040442f190ea42829e28cdd1Eval1InvokerGenerated.evaluate(Unknown Source)
at com.test.drools.Rule_employeeContributionStartDateAfterAccountStartDate_ff664e4a040442f190ea42829e28cdd1Eval1Invoker.evaluate(Unknown Source)
at org.drools.rule.EvalCondition.isAllowed(EvalCondition.java:114)
... 55 more