I have multibranch pipeline job.Pipeline has around 8 stages, out of which 2 stage are parallel and others are in series. Parallel stage has 8 stage that runs in parallel. I have buildDiscarder(logRotator(numToKeepStr:'3')) set in options. Problem I have is, once in a while the build resets removes all builds and artifacts and starts from build 1. This is so annoying.  Not sure if buildDiscarder is causing it or what is triggering this. Also I get concurrent modification exception once in a while. Not sure if the two issues are related or not. 

{{ java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1445)
at java.util.HashMap$EntryIterator.next(HashMap.java:1479)
at java.util.HashMap$EntryIterator.next(HashMap.java:1477)
at com.thoughtworks.xstream.converters.collections.MapConverter.marshal(MapConverter.java:75)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:69)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:43)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:88)
at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution$ConverterImpl.writeChild(CpsFlowExecution.java:1673)
at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution$ConverterImpl.marshal(CpsFlowExecution.java:1618)
at hudson.util.XStream2$AssociatedConverterImpl.marshal(XStream2.java:464)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:69)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:84)
at hudson.util.RobustReflectionConverter.marshallField(RobustReflectionConverter.java:265)
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:252)
Caused: java.lang.RuntimeException: Failed to serialize org.jenkinsci.plugins.workflow.job.WorkflowRun#execution for class org.jenkinsci.plugins.workflow.job.WorkflowRun
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:256)
at hudson.util.RobustReflectionConverter$2.visit(RobustReflectionConverter.java:224)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.visitSerializableFields(Pure}}