Run the following script and abort the build while the sh step is in progress.

node {
  echo 'step 1'
  node {
    echo 'step 2'
    sh 'for i in $(seq 1 100); do echo $i; sleep 1; done'
    echo 'step 3'
  }
  echo 'step 4'
}

Then check the resulting flow graph from build/N/execution/graphViz. It gets the nesting structure all wrong.