Volspotconnect2 - volume level sync issue

[basmeyer]

Issue:
I appears that a volume change set with the Volumio web interface and/or with the appropriate REST API commands does not lead in a new volume setting in the Spotify client. It does the other way round.
When the Spotify client is operated, the volume jump right to the last known level the Spotify client had and it is discarding Volumio's setting.
In other words, volume control does not synchronise properly between these 2.

Replication:
Set volume on the Spotify client low, like on 10%. Set volume in Volumio medium high, like on 50. Then operate the Spotify client with the volume buttons on the device or try to modify to volume with the slider. Immediately it jumps very audibly to the volume on the Spotify client.

Conditions:
Volumio v2.834 on RPi4
HifiBerry DAC+ Pro
Volumio Spotify Connect 2 plugin v1.0.5
Spotify v8.5.81 on iOS

[ashthespy]

Replication:
Set volume on the Spotify client low, like on 10%. Set volume in Volumio medium high, like on 50. Then operate the Spotify client with the volume buttons on the device or try to modify to volume with the slider. Immediately it jumps very audibly to the volume on the Spotify client.

Please share logs -- else it's blind guesswork for me :-)

The normal flow is:
Spotify client ->> Spotify Servers ->> VLS Daeom ->> Volspotconnect2 ->> Volumio backend ->> Volumio Frontend.
So when you your client to 10%, Volumio's UI should also jump to 10%. It looks like this is not the case for you?