I (https://github.com/opensearch-project/opensearch-build) have some jenkins pipelines that rely on YAML manifest files. So they load much YAML. I added classes such as Manifest into groovy code, in which I tried to load such YAML. Given that it's not trivial to add external libraries to Jenkins (os is it? how do I?). My simplest attempt was to use readYaml provided by the pipeline, like so:

class Manifest implements Serializable {
    def data
    Manifest(steps, String filename) {
        steps.echo "this works"
        this.data = steps.readYaml(file: filename)
        // this line is never reached
    }
}

This aborts the script without error in my Jenkins. No security problem, no exception, nothing. Just bails.