java.util.ConcurrentModificationException
  at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:909)
  at java.util.ArrayList$Itr.next(ArrayList.java:859)
  at org.jenkins.plugins.lockableresources.LockableResourcesManager.getAllLabels(LockableResourcesManager.java:136)
  at org.jenkins.plugins.lockableresources.LockableResourcesManager.isValidLabel(LockableResourcesManager.java:131)
  at org.jenkins.plugins.lockableresources.LockStepResource.validate(LockStepResource.java:87)
  at org.jenkins.plugins.lockableresources.LockStep.validate(LockStep.java:138)
  at org.jenkins.plugins.lockableresources.LockStepExecution.start(LockStepExecution.java:38)
  at org.jenkinsci.plugins.workflow.cps.DSL.invokeStep(DSL.java:286)
  at org.jenkinsci.plugins.workflow.cps.DSL.invokeMethod(DSL.java:179)
  at org.jenkinsci.plugins.workflow.cps.CpsScript.invokeMethod(CpsScript.java:122)
  at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:48)
  at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
  at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
  at com.cloudbees.groovy.cps.sandbox.DefaultInvoker.methodCall(DefaultInvoker.java:20)

org.jenkins.plugins.lockableresources.LockableResourcesManager#checkCurrentResourcesStatus
org.jenkins.plugins.lockableresources.LockableResourcesManager#fromName
org.jenkins.plugins.lockableresources.LockableResourcesManager#getAllLabels
org.jenkins.plugins.lockableresources.LockableResourcesManager#getDeclaredResources
org.jenkins.plugins.lockableresources.LockableResourcesManager#getFreeResourceAmount
org.jenkins.plugins.lockableresources.LockableResourcesManager#getResourcesFromBuild
org.jenkins.plugins.lockableresources.LockableResourcesManager#getResourcesFromProject
org.jenkins.plugins.lockableresources.LockableResourcesManager#getResourcesWithLabel
org.jenkins.plugins.lockableresources.LockableResourcesManager#getResourcesMatchingScript