DefaultKnowledgeHelper unable to resolve method in JBoss BRMS

Issue

• A method in the model JAR not being resolved by the KnowledgeAgent during runtime.
• Interestingly, validation of the rule passes from inside the Guvnor interface, so it appears it is able to resolve the method there.
• The DRL definition is similar to:

...
java.math.BigDecimal $val_1 = CustomClass.someMethod1(someval);
java.math.BigDecimal $val_2 = CustomClass.someMethod2(someval);
...

• The error message produced in the logs is as follows:

Exception in thread "main" Exception executing consequence for rule "XYZ" in **.rules: [Error: unable to resolve method: org.drools.base.DefaultKnowledgeHelper.someMethod2(java.math.BigDecimal) [arglength=1]]
[Near : {... *** ....}]
             ^
[Line: 1, Column: 1]
    at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39)
    at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1201)
    at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1126)
    at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1349)
    at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:709)
    at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:673)
    at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:228)
    at aaa.bbb.ccc.main(FrondeRuleAgentTest.java:143)
Caused by: [Error: unable to resolve method: org.drools.base.DefaultKnowledgeHelper.someMethod2(java.math.BigDecimal) [arglength=1]]
[Near : {... *** ....}]
             ^
[Line: 1, Column: 1]
    at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:1079)
    at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:1071)
    at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:987)
    at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:377)
    at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.optimizeAccessor(ReflectiveAccessorOptimizer.java:143)
    at org.mvel2.ast.ASTNode.optimize(ASTNode.java:159)
    at org.mvel2.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:115)
    at org.mvel2.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:38)
    at org.mvel2.ast.TypedVarNode.getReducedValueAccelerated(TypedVarNode.java:70)
    at org.mvel2.MVELRuntime.execute(MVELRuntime.java:85)
    at org.mvel2.compiler.CompiledExpression.getValue(CompiledExpression.java:123)
    at org.mvel2.compiler.CompiledExpression.getValue(CompiledExpression.java:116)
    at org.mvel2.MVEL.executeExpression(MVEL.java:930)
    at org.drools.base.mvel.MVELConsequence.evaluate(MVELConsequence.java:101)
    at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1191)
    ... 6 more