Weird Alexa behaviour on window blinds

I configured a custom Alexa skill to use HA with voice commands.

I am unable to setup my window blinds correctly.
The blinds are processed to Alexa (see image), but I can turn them on (up) or off (down), raise (up) or lower (down) them but if i want them to put them into a specific state like 50% Alexa asks for “which setting” and does nothing.
When I control it within the Alexa App via the control sliders it works as intended.

How am I supposed to configure the window blinds to work properly?

configuration yaml for reference:

alexa:
  smart_home:
    locale: de-DE
    filter:
      include_entities:
        - cover.rolladen_terrasse
    entity_config:
      cover.rolladen_terrasse:
        name: "Rolladen Terrasse"
        description: "Rolladen Terrasse"