for more complex variables that are annotated with @Field, the load step fails to bind the variable into the Script class.

For example:

// a.groovy
import groovy.transform.Field

@Field
def LOADED_BUILD_NUMBER = ${env.BUILD_NUMBER}

return this

// Jenkinsfile
node() {
  def a = load('a.groovy')
  echo(${env.BUILD_NUMBER})
  echo(${a.LOADED_BUILD_NUMBER})
}

This example will fail. However, if you replace ${env.BUILD_NUMBER} with a simple type such as `3`, the load step will succeed.

This seems to be related to the security update in workflow-cps v2.64 and the subsequent regression fix for @Field in v2.71.