The following exception is happening occasionally when starting a pipeline build. The pipeline loads one library with @Library notation (library1), the second library is a global pipeline library (library2). Both pipelines libraries have pipeline library caching enabled. Unclear which condition triggers the exception.

 
Started by upstream project "<project>" build number 158
Resume disabled by user, switching to high-performance, low-durability mode.
Loading library <library1>@320bf54ab1e576e62967a0d50cf4b725fcd9b3ae
Library <library1>@320bf54ab1e576e62967a0d50cf4b725fcd9b3ae is cached. Copying from home.
[Pipeline] Start of Pipeline
[Pipeline] library
Loading library <library2>@master
Library <library2>@master is cached. Copying from home.
Terminating library (id: 3)
[Pipeline] End of Pipeline
java.util.ConcurrentModificationException
at java.base/java.util.TreeMap$PrivateEntryIterator.nextEntry(Unknown Source)
at java.base/java.util.TreeMap$KeyIterator.next(Unknown Source)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.marshal(CollectionConverter.java:74)
at com.thoughtworks.xstream.converters.collections.TreeSetConverter.marshal(TreeSetConverter.java:53)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:68)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:59)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:83)
at hudson.util.RobustReflectionConverter.marshallField(RobustReflectionConverter.java:283)
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:270)
Caused: java.lang.RuntimeException: Failed to serialize org.jenkinsci.plugins.workflow.libs.LibraryRecord#variables for class org.jenkinsci.plugins.workflow.libs.LibraryRecord
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:274)
at hudson.util.RobustReflectionConverter$2.visit(RobustReflectionConverter.java:241)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.visitSerializableFields(PureJavaReflectionProvider.java:174)
at hudson.util.RobustReflectionConverter.doMarshal(RobustReflectionConverter.java:226)
at hudson.util.RobustReflectionConverter.marshal(RobustReflectionConverter.java:163)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:68)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:59)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:44)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:87)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeBareItem(AbstractCollectionConverter.java:94)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeItem(AbstractCollectionConverter.java:66)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeCompleteItem(AbstractCollectionConverter.java:81)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.marshal(CollectionConverter.java:75)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:68)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:59)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:83)
at hudson.util.RobustReflectionConverter.marshallField(RobustReflectionConverter.java:283)
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:270)
Caused: java.lang.RuntimeException: Failed to serialize org.jenkinsci.plugins.workflow.libs.LibrariesAction#libraries for class org.jenkinsci.plugins.workflow.libs.LibrariesAction
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:274)
at hudson.util.RobustReflectionConverter$2.visit(RobustReflectionConverter.java:241)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.visitSerializableFields(PureJavaReflectionProvider.java:174)
at hudson.util.RobustReflectionConverter.doMarshal(RobustReflectionConverter.java:226)
at hudson.util.RobustReflectionConverter.marshal(RobustReflectionConverter.java:163)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:68)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:59)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:44)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:87)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeBareItem(AbstractCollectionConverter.java:94)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeItem(AbstractCollectionConverter.java:66)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.writeCompleteItem(AbstractCollectionConverter.java:81)
at com.thoughtworks.xstream.converters.collections.CollectionConverter.marshal(CollectionConverter.java:75)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:68)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:59)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:83)
at hudson.util.RobustReflectionConverter.marshallField(RobustReflectionConverter.java:283)
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:270)
Also: org.jenkinsci.plugins.workflow.actions.ErrorAction$ErrorId: dc2da7f9-30fe-4f41-b74f-cca4fa879bfc
Caused: java.lang.RuntimeException: Failed to serialize hudson.model.Actionable#actions for class org.jenkinsci.plugins.workflow.job.WorkflowRun
at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:274)
at hudson.util.RobustReflectionConverter$2.visit(RobustReflectionConverter.java:241)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.visitSerializableFields(PureJavaReflectionProvider.java:174)
at hudson.util.RobustReflectionConverter.doMarshal(RobustReflectionConverter.java:226)
at hudson.util.RobustReflectionConverter.marshal(RobustReflectionConverter.java:163)
at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:68)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:59)
at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:44)
at com.thoughtworks.xstream.core.TreeMarshaller.start(TreeMarshaller.java:83)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.marshal(AbstractTreeMarshallingStrategy.java:37)
at com.thoughtworks.xstream.XStream.marshal(XStream.java:1303)
at com.thoughtworks.xstream.XStream.marshal(XStream.java:1292)
at com.thoughtworks.xstream.XStream.toXML(XStream.java:1265)
at hudson.util.XStream2.toXMLUTF8(XStream2.java:386)
at org.jenkinsci.plugins.workflow.support.PipelineIOUtils.writeByXStream(PipelineIOUtils.java:34)
at org.jenkinsci.plugins.workflow.job.WorkflowRun.save(WorkflowRun.java:1251)
at hudson.BulkChange.commit(BulkChange.java:98)
at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.notifyListeners(CpsFlowExecution.java:1577)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$3.run(CpsThreadGroup.java:512)
at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$1.run(CpsVmExecutorService.java:41)
at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:139)
at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:68)
at jenkins.util.ErrorLoggingExecutorService.lambda$wrap$0(ErrorLoggingExecutorService.java:51)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.base/java.lang.Thread.run(Unknown Source)
Finished: FAILURE