Extended image block doesn't output class anymore

The CMS Questions
1

Does 3.6 break those things? I couldn’t find a hint.

This:

title: Vorlage für Seite
status: listed

fields:
  elemente:
    label: Elemente für Blocks
    type: blocks
    fieldsets:
      text:
        label: Text
        type: group
        fieldsets:
          - text

          heading:
            extends: blocks/heading
            fields:
              level:
                default: "h3"
                options:
                    - h2
                    - h3
                    - h4
              customId:
                label: Custom ID
                type: text

          - list
          - quote
          - line

     media:
        label: Media
        type: group
        fieldsets:
           image:
             extends: blocks/image
             fields:
               stil:
                 label: Bildgestaltung
                 type: multiselect
                 options:
                   tiny: tiny
                   small: small
                   medium: medium
                   big: big
                   center: center
                   rounded: rounded
                   right: right
                   left: left
                   portrait: portrait
                   shadow-s: shadow-s
                   shadow-m: shadow-m
                   shadow-l: shadow-
           - video
           - gallery

displays the fields nicely in the panel. But this

    <?= $page->elemente()->toBlocks() ?>

does not output the figure with the class name.

It does in another project with the same setup in 3.5.

2

Which figure? From the image? Where does the classname come from? Please post your block snippet!

3

Thank you… !