Volume adjustment with buttons not the same as slider

[crasyI]

Version:
MMP: 1.16.9
HAOS: 15.2
HA Core & Supervisor: 2025.5.3
HA Frontend: 20250516.0

My MMP Config:
type: custom:mini-media-player entity: media_player.badezimmer_rechts name: Badezimmer action: none hide: name: true power: true icon: true mute: true next: true prev: true artwork: none speaker_group: platform: heos sync_volume: true show_group_count: false expanded: false supports_master: false entities: - entity_id: media_player.badezimmer_links name: Badezimmer links - entity_id: media_player.badezimmer_rechts name: Badezimmer rechts shortcuts: label: Radio column_height: 20 columns: 1 buttons: - type: script name: _ id: script.media_radio_absolute_relax cover: /local/radio/RadioIcon_AbsolutRelax.png - type: script name: _ id: script.media_radio_neue_welle cover: /local/radio/RadioIcon_DieNeueWelle.png - type: script name: _ id: script.media_radio_regenbogen cover: /local/radio/RadioIcon_RadioRegenbogen.png - type: script name: _ id: script.media_radio_swr_3 cover: /local/radio/RadioIcon_SWR3.png toggle_power: false volume_stateless: false volume_step: 2 max_volume: 40 min_volume: 2 group: true source: icon sound_mode: full replace_mute: play_stop info: scroll scale: 1.8

The issue.
If I use the slider to adjust the volume, which as i understoud is to set the “volume_stateless: false”, the volume will set synchronously on both speakers.
However, if the “volume_stateless: true” parameter is set and the buttons are used to change the volume, it only affects at one of the two speakers, despite the “sync_volume: true” parameter remaining.

I also noticed that if I use the HEOS source instead of the radio shortcuts, the pause button no longer works (a message appears that the button is not working).
I had disabled the power button because it doesn’t work when using a shortcut as the source.

many thanks for your work