The usage of package in global variables works fine until I try to use the global variable from different global variables. The second call ended in a java.lang.LinkageError: "attempted duplicate class definition for name"

How to reproduce:

Use the attached project files. Use Jenkinsfile as main test. The library sources function.groovy, greet.groovy and test.groovy are sources of global variables and placed under vars/*. Include the library under the name "jenkins-testcase-lib".

Starting the test results in:
[Pipeline] nodeRunning on
Jenkins
in /var/lib/jenkins/jobs/nested-library-call/workspace[Pipeline] {[Pipeline] stage[Pipeline] { (1. call)[Pipeline] sh[workspace] Running shell script
+ echo Hello master
Hello master[Pipeline] }[Pipeline] // stage[Pipeline] stage[Pipeline] { (2. call)[Pipeline] }[Pipeline] // stage[Pipeline] }[Pipeline] // node[Pipeline] End of Pipelinejava.lang.LinkageError: loader (instance of org/jenkinsci/plugins/workflow/cps/CpsGroovyShell$CleanGroovyClassLoader): attempted duplicate class definition for name: "com/example/jenkins/testcase/function"
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at groovy.lang.GroovyClassLoader.access$400(GroovyClassLoader.java:62)
at groovy.lang.GroovyClassLoader$ClassCollector.createClass(GroovyClassLoader.java:500)
at groovy.lang.GroovyClassLoader$ClassCollector.onClassNode(GroovyClassLoader.java:517)
at groovy.lang.GroovyClassLoader$ClassCollector.call(GroovyClassLoader.java:521)
at org.codehaus.groovy.control.CompilationUnit$17.call(CompilationUnit.java:834)
at org.codehaus.groovy.control.CompilationUnit.applyToPrimaryClassNodes(CompilationUnit.java:1065)
at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:603)
at org.codehaus.groovy.control.CompilationUnit.processPhaseOperations(CompilationUnit.java:581)
at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:558)
at groovy.lang.GroovyClassLoader.doParseClass(GroovyClassLoader.java:298)
at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:268)
at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:254)
at groovy.lang.GroovyClassLoader.recompile(GroovyClassLoader.java:761)
at groovy.lang.GroovyClassLoader.loadClass(GroovyClassLoader.java:718)
at groovy.lang.GroovyClassLoader.loadClass(GroovyClassLoader.java:787)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
at org.jenkinsci.plugins.workflow.cps.CpsGroovyShell$TimingLoader.loadClass(CpsGroovyShell.java:156)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
at groovy.lang.GroovyClassLoader.loadClass(GroovyClassLoader.java:677)
at groovy.lang.GroovyClassLoader.loadClass(GroovyClassLoader.java:787)
at groovy.lang.GroovyClassLoader.loadClass(GroovyClassLoader.java:775)
at org.jenkinsci.plugins.workflow.cps.global.UserDefinedGlobalVariable.getValue(UserDefinedGlobalVariable.java:54)
at org.jenkinsci.plugins.workflow.cps.CpsScript.invokeMethod(CpsScript.java:99)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1213)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1022)
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:42)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:157)
at org.kohsuke.groovy.sandbox.GroovyInterceptor.onMethodCall(GroovyInterceptor.java:23)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:133)
at org.kohsuke.groovy.sandbox.impl.Checker$1.call(Checker.java:155)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:159)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedCall(Checker.java:129)
at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.methodCall(SandboxInvoker.java:17)
at WorkflowScript.run(WorkflowScript:15)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.delegateAndExecute(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:136)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.executeSingleStage(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:494)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.catchRequiredContextForNode(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:262)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.catchRequiredContextForNode(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:260)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.executeSingleStage(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:493)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:214)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.toolsBlock(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:391)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.toolsBlock(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:390)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:212)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withEnvBlock(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:301)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withEnvBlock(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:300)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:211)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withCredentialsBlock(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:339)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withCredentialsBlock(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:338)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:210)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.inDeclarativeAgent(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:424)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.inDeclarativeAgent(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:423)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateStage(jar:file:/var/lib/jenkins/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:208)
at __cps.transform__(Native Method)
at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:57)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:109)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:82)
at sun.reflect.GeneratedMethodAccessor283.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
at com.cloudbees.groovy.cps.impl.ConstantBlock.eval(ConstantBlock.java:21)
at com.cloudbees.groovy.cps.Next.step(Next.java:83)
at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:174)
at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:163)
at org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.use(GroovyCategorySupport.java:122)
at org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:261)
at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:163)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$001(SandboxContinuable.java:19)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:35)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:32)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.runInSandbox(GroovySandbox.java:108)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:32)
at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:174)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:331)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$100(CpsThreadGroup.java:82)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:243)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:231)
at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:64)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:112)
at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Finished: FAILURE