Jenkins fails to resume builds during restarts when the Agent is connected with WebSockets

❯ kubectl logs -f default-728vq
Warning: SECRET is defined twice in command-line arguments and the environment variable
Warning: AGENT_NAME is defined twice in command-line arguments and the environment variable
Nov 04, 2021 7:45:59 PM hudson.remoting.jnlp.Main createEngine
INFO: Setting up agent: default-728vq
Nov 04, 2021 7:45:59 PM hudson.remoting.jnlp.Main$CuiListener <init>
INFO: Jenkins agent is running in headless mode.
Nov 04, 2021 7:45:59 PM hudson.remoting.Engine startEngine
INFO: Using Remoting version: 4.11
Nov 04, 2021 7:45:59 PM org.jenkinsci.remoting.engine.WorkDirManager initializeWorkDir
INFO: Using /home/jenkins/agent/remoting as a remoting work directory
Nov 04, 2021 7:45:59 PM org.jenkinsci.remoting.engine.WorkDirManager setupLogging
INFO: Both error and output logs will be printed to /home/jenkins/agent/remoting
Nov 04, 2021 7:46:00 PM hudson.remoting.jnlp.Main$CuiListener status
INFO: WebSocket connection open
Nov 04, 2021 7:46:00 PM hudson.remoting.jnlp.Main$CuiListener status
INFO: Connected
Nov 04, 2021 7:46:27 PM hudson.remoting.jnlp.Main$CuiListener status
INFO: Write side closed
Nov 04, 2021 7:46:27 PM hudson.remoting.jnlp.Main$CuiListener status
INFO: Read side closed
Nov 04, 2021 7:46:27 PM hudson.remoting.jnlp.Main$CuiListener status
INFO: Terminated
Nov 04, 2021 7:46:27 PM hudson.remoting.jnlp.Main$CuiListener status
INFO: Read side closed
Nov 04, 2021 7:46:27 PM hudson.remoting.jnlp.Main$CuiListener status
INFO: Read side closed
Nov 04, 2021 7:46:27 PM hudson.remoting.jnlp.Main$CuiListener status
INFO: http://jenkins.default.svc.cluster.local:8080/login is not ready: 503
Nov 04, 2021 7:46:38 PM hudson.remoting.Engine lambda$new$1
SEVERE: Uncaught exception in Engine thread Thread[Thread-0,5,main]
java.lang.NoClassDefFoundError: jenkins/slaves/restarter/JnlpSlaveRestarterInstaller
        at jenkins.slaves.restarter.JnlpSlaveRestarterInstaller$FindEffectiveRestarters$1.onReconnect(JnlpSlaveRestarterInstaller.java:91)
        at hudson.remoting.EngineListenerSplitter.onReconnect(EngineListenerSplitter.java:54)
        at hudson.remoting.Engine.runWebSocket(Engine.java:687)
        at hudson.remoting.Engine.run(Engine.java:496)
Caused by: java.lang.ClassNotFoundException: jenkins.slaves.restarter.JnlpSlaveRestarterInstaller
        at java.base/java.net.URLClassLoader.findClass(Unknown Source)
        at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:215)
        at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
        at java.base/java.lang.ClassLoader.loadClass(Unknown Source)
        ... 4 more

$ kind create cluster

$ helm repo add jenkins https://charts.jenkins.io

$ helm repo update

$ helm upgrade jenkins jenkins/jenkins --install --wait --debug -f- <<'EOF'
controller:
  adminPassword: admin
  agentListenerEnabled: false
  # specifying plugins without version makes sure to use the latest
  installPlugins:
    - kubernetes
    - workflow-aggregator
    - git
    - configuration-as-code
    - job-dsl
    - saferestart
  JCasC:
    configScripts:
      my-jobs: |
        jobs:
          - script: |
              pipelineJob('testjob') {
                definition {
                  cps {
                    script("""\
                      pipeline {
                        agent any
                        stages {
                          stage ('test') {
                            steps {
                              sleep 1000
                            }
                          }
                        }
                      }""".stripIndent())
                    sandbox()
                  }
                }
              }
agent:
  websocket: true
  tag: 4.11-1
EOF

$ echo http://127.0.0.1:8080 && kubectl --namespace default port-forward svc/jenkins 8080:8080