I just made January 2020 update. Before, when I was changing volume from the official remote (or from TV remote), my AV-receiver was changing volume.
From now I have to go to CEC settings and de-activate (and/or activate) the CEC in order to have it working. (yes, it works even if CEC is deactivated !!!)
When it doesn’t work, volume button change volume on Vero 4K+, not on my AV-receiver.