During a training on Blue Ocean, one of our instance faced a weird error.

After sucessfully building a pipeline (so valid Jenkinsfile), all tries to edit the pipeline using the Blue Ocean editor ends with the following error message: "Error loading Pipeline".

See the attached "editor-error.png".

The Jenkinsfile is valid and builds sucessfully. Its content is the following:

pipeline {
  agent any
  stages {
    stage('Buzz Buzz') {
      steps {
        echo 'Bees Buzz!'
        echo 'Bees Buzz'
        echo 'new buzz'
        echo 'bees bees'
      }
    }
    stage('Bees Bees') {
      steps {
        echo 'Buzz, Bees, Buzz'
      }
    }
  }
}

The Multi Branch Pipeline project was in a weird state: the "Scan" button in the Classic UI was absent (see the screenshots "jenkins-homepage.png" and "mb-job-page.png"), while the default user is administrator and has all rights.

This "Pipeline" had been created using the Blue Ocean "New Pipeline Wizard", on a Git Repository, using SSH.

No configurations shifts looked like to have been occured between this instance and the others (the user never left Blue Ocean and don't even know what is the "Manage" page).

I've attached a CloudBees support bundle, the Jenkins Logs output might help (the data inside is not sensitive so you got everything).