Stapler JRebel used to support hot reloading of classes when developing Jenkins in some conditions.: https://wiki.jenkins.io/display/JENKINS/Developing+with+JRebel . This flow has not been used for long time, and it is unlikely that it can operate properly anymore.  I suggest removing the dependency on JRebel to reduce the Jenkins core size and to prevent transitive dependency issues.

Example of a transitive dependency involving JRebel:
Require upper bound dependencies error for com.google.guava:guava:11.0.1 paths to dependency are:
+-com.cloudbees.codeship.jenkins-support:jenkins-pipeline-step-maven:1.0-beta-19
+-io.jenkins.jenkinsfile-runner:setup:1.0-beta-19
+-org.jenkins-ci.main:jenkins-core:2.249.1
+-com.google.guava:guava:11.0.1
and
+-com.cloudbees.codeship.jenkins-support:jenkins-pipeline-step-maven:1.0-beta-19
+-io.jenkins.jenkinsfile-runner:setup:1.0-beta-19
+-org.jenkins-ci.main:jenkins-core:2.249.1
+-org.kohsuke.stapler:stapler-jrebel:1.260
+-org.kohsuke.stapler:stapler:1.260
+com.google.guava:guava:11.0.1 (managed) <- com.google.guava:guava:27.1-jre