I have recently lost the ability to control the balance of my rears, when used as rear surrounds. Sonos have told me that the only way to restore the balance control is to separate them from the room as surrounds. When set up in trueplay mode or not they, the rears, are out of balance which makes listening to music terrible. This can’t be correct. Can it?
There is no setting to adjust the balance of rear speakers and never has been. But they should not be out of balance so you need to pursue why that is happening on your system.