Operators NPE

2022-22-11 14:03:23.162 | ERROR | Operators | Operator called default onErrorDropped
reactor.core.Exceptions$ErrorCallbackNotImplemented: java.lang.NullPointerException
Caused by: java.lang.NullPointerException
at io.emeraldpay.dshackle.upstream.ForkWatch.start$lambda-7(ForkWatch.kt:110) ~[classes/:?]
at reactor.core.publisher.MonoFlatMapMany$FlatMapManyMain.onNext(MonoFlatMapMany.java:163) [reactor-core-3.4.10.jar:3.4.10]
at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82) [reactor-core-3.4.10.jar:3.4.10]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.tryEmitScalar(FluxFlatMap.java:488) [reactor-core-3.4.10.jar:3.4.10]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.onNext(FluxFlatMap.java:421) [reactor-core-3.4.10.jar:3.4.10]
at reactor.core.publisher.FluxInterval$IntervalRunnable.run(FluxInterval.java:125) [reactor-core-3.4.10.jar:3.4.10]
at reactor.core.scheduler.PeriodicWorkerTask.call(PeriodicWorkerTask.java:59) [reactor-core-3.4.10.jar:3.4.10]
at reactor.core.scheduler.PeriodicWorkerTask.run(PeriodicWorkerTask.java:73) [reactor-core-3.4.10.jar:3.4.10]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?]
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305) [?:?]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305) [?:?]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
at java.lang.Thread.run(Thread.java:830) [?:?]

dshackle version 0.13.1
launch command
java -XX:MinRAMPercentage=55.0 -XX:MaxRAMPercentage=85.0 -XX:NativeMemoryTracking=summary -cp /app/resources:/app/classes:/app/libs/* io.emeraldpay.dshackle.StarterKt