Media_player from fully kiosk integration can't stop the stream

Hi everyone,

installed a Fire HD 8 as a dashboard for my Homeassistant with Fully Kiosk. Now I want to play an internet radio stream over the media_player entity from the fully Kiosk. This works fine:

  - service: media_player.play_media
    target:
      device_id: f14bda651e711b4cac6ef28994f50298
    data:
      media_content_id: http://stream.srg-ssr.ch/m/rsp/mp3_128
      media_content_type: MUSIC

But I couldn’t find a solution how to stop the stream. Following code didn’t work even with pause or turn off.

  - service: media_player.media_stop
    target:
      entity_id: media_player.fire_tablet_media_player

Would really appreciate your help.