Volume increase/decrease not changing when plugged in via USB

[Gareth2665]

Ive just noticed that my phones volume increase / decrease no longer works when plugged into my head iunit via USB.

The slider does visibly move up and down but makes no change to the volume of the head unit.  It used to work and was a better sound when the phones volume was turned up full then controlled further with the head unit volume control.

If I dont plug the phone in via USB and use Bluetooth to the head unit the volume buttons works as normal with either Spotify or Samsung music.

I assume this has happened in an update so does anyone have any idea how to get it back working?

[Tourbillon De La Vie]

Try running diagnostic, USB connection, via Samsung members app 

[Gareth2665]

I did run the diagnostics that were fine. However i'm 100% sure its not a fault rather something has been changed with an update.

If i play music or just adjust the volume on the handset it works fine and adjusts. If i plug it into the vans' usb and no music is playing on the head unit the volume control still works.

However, as soon as i press Play on a music app to start playing music and then try the volume slider it moves up and down but makes no difference to the volume.

For example, I plug the USB into the head unit and Android Auto comes on but is not yet playing music. Press the volume slider and it works. As soon as I press play on the screens Spotify APP and music plays the volume slider does not change the volume.