Unable to make field private final java.util.Comparator java.util.TreeMap.comparator accessible: module java.base does not "opens java.util" to unnamed module @425ea9cb

Building remotely on Windows10 in workspace c:\jenkins\workspace\SELENIUM Single-Browser Automated Test
hudson.remoting.ProxyException: java.lang.reflect.InaccessibleObjectException: Unable to make field private final java.util.Comparator java.util.TreeMap.comparator accessible: module java.base does not "opens java.util" to unnamed module @425ea9cb
    at java.lang.reflect.AccessibleObject.checkCanSetAccessible(Unknown Source)
    at java.lang.reflect.AccessibleObject.checkCanSetAccessible(Unknown Source)
    at java.lang.reflect.Field.checkCanSetAccessible(Unknown Source)
    at java.lang.reflect.Field.setAccessible(Unknown Source)
    at com.thoughtworks.xstream.core.util.Fields.locate(Fields.java:39)
    at com.thoughtworks.xstream.converters.collections.TreeMapConverter.<clinit>(TreeMapConverter.java:50)
Also:   hudson.remoting.Channel$CallSiteStackTrace: Remote call to JNLP4-connect connection from ip-172-20-68-132.eu-central-1.compute.internal/172.20.68.132:42200
        at hudson.remoting.Channel.attachCallSiteStackTrace(Channel.java:1741)
        at hudson.remoting.UserRequest$ExceptionResponse.retrieve(UserRequest.java:357)
        at hudson.remoting.Channel.call(Channel.java:955)
        at hudson.FilePath.act(FilePath.java:1072)
        at hudson.FilePath.act(FilePath.java:1061)
        at org.jenkinsci.plugins.gitclient.Git.getClient(Git.java:144)
        at hudson.plugins.git.GitSCM.createClient(GitSCM.java:822)
        at hudson.plugins.git.GitSCM.createClient(GitSCM.java:813)
        at hudson.plugins.git.GitSCM.checkout(GitSCM.java:1186)
        at hudson.scm.SCM.checkout(SCM.java:504)
        at hudson.model.AbstractProject.checkout(AbstractProject.java:1208)
        at hudson.model.AbstractBuild$AbstractBuildExecution.defaultCheckout(AbstractBuild.java:574)
        at jenkins.scm.SCMCheckoutStrategy.checkout(SCMCheckoutStrategy.java:86)
        at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:499)
        at hudson.model.Run.execute(Run.java:1810)
        at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:543)
        at hudson.model.ResourceController.execute(ResourceController.java:97)
        at hudson.model.Executor.run(Executor.java:429)
Caused: hudson.remoting.ProxyException: java.lang.ExceptionInInitializerError
    at com.thoughtworks.xstream.XStream.setupConverters(XStream.java:811)
    at com.thoughtworks.xstream.XStream.<init>(XStream.java:574)
    at com.thoughtworks.xstream.XStream.<init>(XStream.java:496)
    at com.thoughtworks.xstream.XStream.<init>(XStream.java:465)
    at com.thoughtworks.xstream.XStream.<init>(XStream.java:411)
    at com.thoughtworks.xstream.XStream.<init>(XStream.java:378)
    at hudson.util.XStream2.<init>(XStream2.java:113)
    at hudson.ProxyConfiguration.<clinit>(ProxyConfiguration.java:308)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at com.sun.proxy.$Proxy10.<clinit>(Unknown Source)
    at jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at java.lang.reflect.Proxy.newProxyInstance(Unknown Source)
    at java.lang.reflect.Proxy.newProxyInstance(Unknown Source)
    at hudson.remoting.RemoteInvocationHandler.wrap(RemoteInvocationHandler.java:167)
    at hudson.remoting.Channel.export(Channel.java:768)
    at hudson.remoting.Channel.export(Channel.java:731)
    at org.jenkinsci.plugins.gitclient.LegacyCompatibleGitAPIImpl.writeReplace(LegacyCompatibleGitAPIImpl.java:198)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at java.io.ObjectStreamClass.invokeWriteReplace(Unknown Source)
    at java.io.ObjectOutputStream.writeObject0(Unknown Source)
    at java.io.ObjectOutputStream.writeObject(Unknown Source)
    at hudson.remoting.UserRequest._serialize(UserRequest.java:264)
    at hudson.remoting.UserRequest.serialize(UserRequest.java:273)
    at hudson.remoting.UserRequest.perform(UserRequest.java:223)
    at hudson.remoting.UserRequest.perform(UserRequest.java:54)
    at hudson.remoting.Request$2.run(Request.java:369)
    at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:72)