I have this issue too. Not sure if it's the same model, but I also have a Sony BRAVIA with Google connected to a Denon AVR.
What I have found as a somewhat annoying workaround is to change the volume on the TV with slow, deliberate presses of the volume buttons. If I hold down the volume button the AVR can't 'keep up' and the volume doesn't change as much on the AVR as it does on the TV. Slow presses of the volume buttons allow the AVR and TV to keep the volume in sync.
I have this issue too. Not sure if it's the same model, but I also have a Sony BRAVIA with Google connected to a Denon AVR.
What I have found as a somewhat annoying workaround is to change the volume on the TV with slow, deliberate presses of the volume buttons. If I hold down the volume button the AVR can't 'keep up' and the volume doesn't change as much on the AVR as it does on the TV. Slow presses of the volume buttons allow the AVR and TV to keep the volume in sync.