Wrong blueprint rendering

Given the following markup:

title: Site
tabs:
  main:
    label: Content
    columns:
      - width: 1/2
        sections:
          articles: sections/articles
      
  banner:
    label: Banner
    columns:
      - width: 1/2
        sections:
          content:
            type: fields
            fields:
              showBanner:
                label: Banner anzeigen
                type: toggle
      - width: 1/2  
        sections:
          content:
            type: fields
            fields:
              bannertext:
                label: Bannertext
                type: textarea
                buttons: false
              referencedArticle:
                type: pages
                label: Artikel
                multiple: false
                query: site.find('blog')
                subpages: false

Why does it render like this:

Because you use two sections with the same key content. Keys must be unique.

You can also skip the fields sections completely:

banner:
  label: Banner
  columns:
    - width: 1/2
      fields:
        showBanner:
          label: Banner anzeigen
          type: toggle
    - width: 1/2
      fields:
        bannertext:
          label: Bannertext
          type: textarea
          buttons: false
        referencedArticle:
          type: pages
          label: Artikel
          multiple: false
          query: site.find('blog')
          subpages: false