Genetic Evolution error: Comparison method violates its general contract

10:34:48.247 [Nonblocking computeThread - 151 - GPIslandJob_7] ERROR c.s.g.c.p.MultithreadComputePerformer - Error while running task: GPIslandJob_7(962260))
java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.base/java.util.TimSort.mergeHi(TimSort.java:903) ~[na:na]
at java.base/java.util.TimSort.mergeAt(TimSort.java:520) ~[na:na]
at java.base/java.util.TimSort.mergeCollapse(TimSort.java:448) ~[na:na]
at java.base/java.util.TimSort.sort(TimSort.java:245) ~[na:na]
at java.base/java.util.Arrays.sort(Arrays.java:1515) ~[na:na]
at java.base/java.util.ArrayList.sort(ArrayList.java:1749) ~[na:na]
at java.base/java.util.Collections.sort(Collections.java:177) ~[na:na]
at com.strategyquant.tradinglib.gp.GPGenerationalEngine.sortEvaluatedPopulation(Unknown Source) ~[SQTradingLib.jar:na]
at com.strategyquant.tradinglib.gp.GPGenerationalEngine.nextEvolutionStep(Unknown Source) ~[SQTradingLib.jar:na]
at com.strategyquant.tradinglib.gp.GPGenerationalEngine.gpEvolution(Unknown Source) ~[SQTradingLib.jar:na]
at com.strategyquant.tradinglib.gp.GPGenerationalEngine.evolve(Unknown Source) ~[SQTradingLib.jar:na]
at com.strategyquant.tradinglib.gp.GPIslandJob.call(Unknown Source) ~[SQTradingLib.jar:na]
at com.strategyquant.tradinglib.gp.GPIslandJob.call(Unknown Source) ~[SQTradingLib.jar:na]
at com.strategyquant.gridlib.compute.performer.MultithreadComputePerformer$1.run(Unknown Source) ~[SQGridLib2.jar:na]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) ~[na:na]
at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]