When running the below pipeline if I have 2 agents that are available and are using the RH7 label then everything completes as expected. However If I only have 1 available agent on the RH7 label either because the other agents are busy or offline then the job will fail with the below error message. Every machine on the RH7 label has a single executor.

Additionally whilst the job is marked as failed, the agent that tried to run the job still shows it as running. I don't know if it would eventually time out but after a few minutes it still shows the job "running" in the executor window. Cancelling the job in the executor window returns the agent to a usable state.

Pipeline:

#!groovy

pipeline {
    agent none

    stages {
        stage ("p") {
            parallel {
                stage ("p1") {
                    agent { label "RH7" }

                    stages {
                        stage ("p1s1") {
                            steps {
                                echo "Hello in p1s1"
                            }
                        }

                        stage ("p1s2") {
                            steps {
                                echo "Hello in p1s2"
                            }
                        }
                    }
                }

                stage ("p2") {
                    agent { label "RH7" }

                    stages {
                        stage ("p2s1") {
                            steps {
                                echo "Hello in p2s1"
                            }
                        }
                    }
                }
            }
        }
    }
}

Error Message:

Running in Durability level: MAX_SURVIVABILITY
[Pipeline] stage
[Pipeline] { (p)
[Pipeline] parallel
[Pipeline] [p1] { (Branch: p1)
[Pipeline] [p2] { (Branch: p2)
[Pipeline] [p1] stage
[Pipeline] [p1] { (p1)
[Pipeline] [p2] stage
[Pipeline] [p2] { (p2)
[Pipeline] [p1] node
[p1] Running on Red Hat 7 - 2 in /jenkins/workspace/Problem@2
[Pipeline] [p2] node
[Pipeline] [p1] {
[Pipeline] [p1] stage
[Pipeline] [p1] { (p1s1)
[Pipeline] [p1] echo
[p1] Hello in p1s1
[Pipeline] [p1] }
[Pipeline] [p1] // stage
[Pipeline] [p1] stage
[Pipeline] [p1] { (p1s2)
[Pipeline] End of Pipeline
java.lang.StackOverflowError
at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:111)
at org.jboss.marshalling.river.RiverMarshaller.doWriteFields(RiverMarshaller.java:1032)
at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:988)
at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:854)
at org.jboss.marshalling.river.RiverMarshaller.doWriteFields(RiverMarshaller.java:1032)
at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:988)
TRUNCATED SEE ATTACHED LOG

Also within the system log there is the following additional error:

Aug 09, 2018 9:11:10 PM WARNING org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService reportProblem

Unexpected exception in CPS VM thread: CpsFlowExecutionOwner[Problem/39:Problem #39
java.lang.IllegalStateException: JENKINS-50407: no loaded shell in CpsFlowExecutionOwner[Problem/39:Problem #39
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:52)
at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:174)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:332)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$200(CpsThreadGroup.java:83)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:244)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:232)
at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:64)
at java.util.concurrent.FutureTask.run(Unknown Source)
at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:131)
at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

If there is any additional information you require please let me know.