optaplanner-core/src/main/java/org/optaplanner/core/impl/score/director/drools/DroolsScoreDirector.java
@Override
    public void afterProblemFactRemoved(Object problemFact) {
        FactHandle factHandle = kieSession.getFactHandle(problemFact);
        if (factHandle == null) {
            throw new IllegalArgumentException("The problemFact (" + problemFact
                    + ") was never added to this ScoreDirector.\n"
                    + "Maybe that specific instance is not in the "
                    + PlanningSolution.class.getSimpleName() + "'s problem fact members ("
                    + getSolutionDescriptor().getProblemFactMemberAndProblemFactCollectionMemberNames() + ").\n"
                    + "Maybe first translate that external instance to the workingSolution's instance"
                    + " with " + ScoreDirector.class.getSimpleName() + ".lookUpWorkingObject().");
        }
        kieSession.delete(factHandle);
        super.afterProblemFactRemoved(problemFact);
    }
@Override
    public void afterProblemFactRemoved(Object problemFact) {
        FactHandle factHandle = kieSession.getFactHandle(problemFact);
        if (factHandle == null) {
            throw new IllegalArgumentException("The problemFact (" + problemFact
                    + ") was never added to this ScoreDirector.\n"
                    + "Maybe that specific instance is not in the "
                    + PlanningSolution.class.getSimpleName() + "'s problem fact members ("
                    + getSolutionDescriptor().getProblemFactMemberAndProblemFactCollectionMemberNames() + ").\n"
                    + "Maybe first translate that external instance to the workingSolution's instance"
                    + " with " + ScoreDirector.class.getSimpleName() + ".lookUpWorkingObject().");
        }
        kieSession.delete(factHandle);
        super.afterProblemFactRemoved(problemFact);
    }
public void beforeProblemFactRemoved(Object problemFact) // Do nothing