Floorplan-card - problems with class assignment

Hi everyone,
I recently started using Home Assistant and I am an absolute beginner. I use the floorplan card to display status information (doors, windows, roller shutter, …). It works perfectly with doors and windows. However, I have problems with the roller shutter and the attribute current_position. The attribute exists and also has a value (see screenshots).
grafik

In the YAML code, however, the attribute does not seem to be assigned a value: it fires “if position is none” with class test-case (marked with color red in the screenshot).

  rules:
    - element: Button-Steckdose-Brunnen-Symbol
      entity: switch.knx_brunnen
      state_action:
        service: floorplan.class_set
        service_data: switch-${entity.state}
      tap_action: toggle
    - element: floorplan.eg-az-fenster
      entity: binary_sensor.eg_az_fenster
      state_action:
        service: floorplan.class_set
        service_data:
          class: '${(entity.state === "on") ? "window-open" : "window-closed"}'
    - element: floorplan.eg-az-rolo
      entity: cover.eg_arbeit_rolo
      state_action:
        service: floorplan.class_set
        service_data:
          class: >
            {% set position = state_attr(cover.eg_arbeit_rolo, 'current_position') %}
            {% if position is none %}
              test-case
            {% elif position == 0 %}
              cover-closed
            {% elif position == 100 %}
              cover-open
            {% else %}
              cover-mid
            {% endif %}​

Does anyone have an idea what I am doing wrong? Seems that my way to access the elements attribute is wrong - even if it works in the Template-Editor … Any idea to solve this?

Thanks and best regards
Tom

It was probably a silly post: Defining helpers is enough, then of course it works with access to current_position.