DLNA mediaplayer: weird issues

Hi all
I have a spare tradfri remote, so I wanted to use it to turn up/down the volume.
I created the automation and it works.
but…
the service volume_up (or down) can only be called once, a second time will not do anything.
the set_volume service seems to work as expected for a fixed value. If I try to
{{state_attr("media_player.luidspreker", "volume_level") + 0.1}} it will only go up once.
the volume_level in developer tools / states never changes from 0.57.
the volume slider in the device will not change.

using the slider will allow me to increase the volume in steps.

I’m thinking I must be doing something wrong here? though it might be my speaker that f.e. doesn’t have a stop nor pause command, I can only stop it by selecting an invalid source.

alias: ZilverRemote
description: ""
trigger:
  - platform: event
    event_type: deconz_event
    event_data:
      device_id: 222bd9cb30d72414fd1ff0550977bcb9
condition: []
action:
  - service: persistent_notification.create
    data:
      message: zilverremote {{ trigger.event.data.event }}
    enabled: false
  - choose:
      - conditions:
          - condition: template
            value_template: "{{ trigger.event.data.event == 1002}}"
        sequence:
          - service: media_player.volume_up
            data: {}
            target:
              device_id: 8cf1b8f40fc8c97822551f389a95cb16
      - conditions:
          - condition: template
            value_template: "{{ trigger.event.data.event == 2002}}"
        sequence:
          - service: media_player.volume_down
            data: {}
            target:
              device_id: 8cf1b8f40fc8c97822551f389a95cb16
      - conditions:
          - condition: template
            value_template: "{{ trigger.event.data.event == 3002}}"
        sequence:
          - service: media_player.volume_set
            data:
              volume_level: >-
                {{state_attr("media_player.luidspreker", "volume_level") +
                0.1}}
            target:
              device_id: 8cf1b8f40fc8c97822551f389a95cb16
      - conditions:
          - condition: template
            value_template: "{{ trigger.event.data.event == 4002}}"
        sequence:
          - service: media_player.volume_set
            data:
              volume_level: >-
                {{state_attr("media_player.luidspreker", "volume_level") +
                0.2}}
            target:
              device_id: 8cf1b8f40fc8c97822551f389a95cb16
mode: single