Right, the root of the behavior is that TRACE enables assertWorkingScore(), which tells me that the workingScore (reflecting the score after the move) is not the same as the uncorruptedScore (reflecting prior to the change), and specifically, that 4 ConstraintOccurrences are mismatched. For some reason, new I looked, along the lines of Christopher's earlier suggestion, that equals() was the issue, but it was not. It just appears that insertLogical() is not replacing the ConstraintOccurences that were associated with the PlanningVariable's class. Jon -- View this message in context: http://drools.46999.n3.nabble.com/drools-planner-5-4-0-Final-java-lang-Il... Sent from the Drools: User forum mailing list archive at Nabble.com.