Looks like an unintended side effect here of showing the end steps for blocks, but run the following pipeline:

stage('sample') {
    node {
        dir('sample') {
            dir('more') {
                sh 'failme'
            }
        }
    }
}

Then mouseover the stage and look at the popup, which will now extend above the top of the screen and show some serious ugliness (see screenshot).