IllegalStateException is thrown if there is CompositeMove on a chained planning variable created by CartesianProductMoveSelector:

Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Solving failed.
at org.optaplanner.examples.common.swingui.SolverAndPersistenceFrame$SolveWorker.done(SolverAndPersistenceFrame.java:382)
at javax.swing.SwingWorker$5.run(SwingWorker.java:737)
at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:832)
at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:112)
at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:842)
at javax.swing.Timer.fireActionPerformed(Timer.java:313)
at javax.swing.Timer$DoPostEvent.run(Timer.java:245)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

Caused by: java.lang.IllegalStateException: The entity (Customer-7) has a variable (previousStandstill) with value (Customer-33) which has a sourceVariableName variable (nextCustomer) with a value (Customer-5) which is not null.
Verify the consistency of your input problem for that sourceVariableName variable.
at org.optaplanner.core.impl.domain.variable.inverserelation.SingletonInverseVariableListener.insert(SingletonInverseVariableListener.java:72)
at org.optaplanner.core.impl.domain.variable.inverserelation.SingletonInverseVariableListener.afterVariableChanged(SingletonInverseVariableListener.java:51)
at org.optaplanner.core.impl.domain.variable.listener.support.VariableListenerSupport.triggerVariableListenersInNotificationQueues(VariableListenerSupport.java:209)
at org.optaplanner.core.impl.score.director.AbstractScoreDirector.triggerVariableListeners(AbstractScoreDirector.java:261)
at org.optaplanner.core.impl.heuristic.move.AbstractMove.doMove(AbstractMove.java:36)
at org.optaplanner.core.impl.heuristic.move.AbstractMove.doMove(AbstractMove.java:30)
at org.optaplanner.core.impl.heuristic.move.CompositeMove.doMove(CompositeMove.java:108)
at org.optaplanner.core.impl.heuristic.move.CompositeMove.doMove(CompositeMove.java:37)
at org.optaplanner.core.impl.score.director.AbstractScoreDirector.doAndProcessMove(AbstractScoreDirector.java:189)
at org.optaplanner.core.impl.localsearch.decider.LocalSearchDecider.doMove(LocalSearchDecider.java:132)
at org.optaplanner.core.impl.localsearch.decider.LocalSearchDecider.decideNextStep(LocalSearchDecider.java:116)
at org.optaplanner.core.impl.localsearch.DefaultLocalSearchPhase.solve(DefaultLocalSearchPhase.java:70)
at org.optaplanner.core.impl.solver.AbstractSolver.runPhases(AbstractSolver.java:88)
at org.optaplanner.core.impl.solver.DefaultSolver.solve(DefaultSolver.java:191)
at org.optaplanner.examples.common.business.SolutionBusiness.solve(SolutionBusiness.java:329)
at org.optaplanner.examples.common.swingui.SolverAndPersistenceFrame$SolveWorker.doInBackground(SolverAndPersistenceFrame.java:370)
at javax.swing.SwingWorker$1.call(SwingWorker.java:295)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at javax.swing.SwingWorker.run(SwingWorker.java:334)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)