Jenkins CascadeChoiceParameter not rendering from Jenkinsfile

Question

The following CascaseChoiceParamater code in a Jenkinsfile does not render a reactive parameter. Same code renders fine using a Jenkins pipeline script. (where it was successfully tested). Any ideas?

[$class: 'CascadeChoiceParameter', name: 'TARGET_HOST', choiceType: 'PT_SINGLE_SELECT', description: 'Target Server', filterLength: 1, filterable: false, randomName: 'choice-parameter-38222740232420', referencedParameters: 'ENV', script: [ $class: 'GroovyScript', fallbackScript: [ classpath: [], sandbox: false, script: "return['Nothing']" ], script: [ classpath: [], sandbox: false, script: '''if (ENV.equals("PROD")) { return ["RXBK1","RXBK2","ALL"] } else if (ENV.equals("UAT")) { return ["RXDV1","RXBK1UAT","RXBK2UAT","ALL"] } else if (ENV.equals("QA")) { return ["RXDV1","RXBK1QA","RXBK2QA","ALL"] } else if (ENV.equals("DEV")) {return ["RXDV1"] } ''' ] ] ],

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