[rules-users] [OptaPlanner] conflict Resolver 'org.drools.core.conflict.DepthConflictResolver' not found

Hi, I am using planner 6.0.0.beta5. to schedule some kind of events like in curriculum example, and created web front end for this using Vaadin. but for some reason some users (only few) from this web client get this exception (at the end) and scheduler fails. What could have been the cause for this? the code I have is as follows. SolverFactory solverFactory = new XmlSolverFactory( "/org/optaplanner/examples/curriculumcourse/solver/curriculumCourseSolverConfig.xml"); TerminationConfig tc = solverFactory.getSolverConfig().getTerminationConfig(); tc.setMaximumSecondsSpend(120L); Solver solver = solverFactory.buildSolver(); creating the solver is throwing the exception. log: *java.lang.IllegalArgumentException: conflict Resolver 'org.drools.core.conflict.DepthConflictResolver' not found at org.drools.core.RuleBaseConfiguration.determineConflictResolver(RuleBaseConfiguration.java:866) ~[drools-core-6.0.0.Beta5.jar:6.0.0.Beta5] at org.drools.core.RuleBaseConfiguration.init(RuleBaseConfiguration.java:455) ~[drools-core-6.0.0.Beta5.jar:6.0.0.Beta5] at org.drools.core.RuleBaseConfiguration.init(RuleBaseConfiguration.java:411) ~[drools-core-6.0.0.Beta5.jar:6.0.0.Beta5] at org.drools.core.RuleBaseConfiguration.<init>(RuleBaseConfiguration.java:262) ~[drools-core-6.0.0.Beta5.jar:6.0.0.Beta5] at org.drools.compiler.kie.builder.impl.KieServicesImpl.newKieBaseConfiguration(KieServicesImpl.java:146) ~[drools-compiler-6.0.0.Beta5.jar:6.0.0.Beta5] at org.optaplanner.core.config.score.director.ScoreDirectorFactoryConfig.buildKieBase(ScoreDirectorFactoryConfig.java:330) ~[optaplanner-core-6.0.0.Beta5.jar:6.0.0.Beta5] at org.optaplanner.core.config.score.director.ScoreDirectorFactoryConfig.buildDroolsScoreDirectorFactory(ScoreDirectorFactoryConfig.java:280) ~[optaplanner-core-6.0.0.Beta5.jar:6.0.0.Beta5] at org.optaplanner.core.config.score.director.ScoreDirectorFactoryConfig.buildScoreDirectorFactory(ScoreDirectorFactoryConfig.java:187) ~[optaplanner-core-6.0.0.Beta5.jar:6.0.0.Beta5] at org.optaplanner.core.config.score.director.ScoreDirectorFactoryConfig.buildScoreDirectorFactory(ScoreDirectorFactoryConfig.java:175) ~[optaplanner-core-6.0.0.Beta5.jar:6.0.0.Beta5] at org.optaplanner.core.config.solver.SolverConfig.buildSolver(SolverConfig.java:145) ~[optaplanner-core-6.0.0.Beta5.jar:6.0.0.Beta5] at org.optaplanner.core.config.solver.XmlSolverFactory.buildSolver(XmlSolverFactory.java:104) ~[optaplanner-core-6.0.0.Beta5.jar:6.0.0.Beta5]* -- Regards, Sandeep Bandela.