Editor.Panels.addPanel duplicate buttons

While creating a custom plugin, in case, when editor.Panels.addPanel is using inside plugin function - buttons are duplicated.

Example: https://jsfiddle.net/kncdah8b/

Buttons are not duplicated:

• when using single Panels.addButton API while loop buttons separately
• when adding panel after editor const editor = grapesjs.init({}) has been created

Currently, I'm using the next trick to avoid the duplications:

function gjsPlugin(editor) {
  editor.on('load', () => {
    editor.Panels.addPanel({
      id: 'custom-panel',
      el: '.custom-panel',
      buttons: [
        {
          id: 'PANEL_ACTION.EXPT',
          className: 'fa fa-code',
          command: 'export-template',
          attributes: { title: 'View code' }
        }
      ]
    });
  });
}