I no longer have another source but when I add Sonos back to my previous system everything is perfectly balanced left-to-right via either setting the Sonos equalizer to 'center' or when not running the equalizer and setting Sonos volume to 'fixed.' On the Devialet however both these settings result in a 16-20% higher bias to right speaker (or perhaps its 16-20% lower bias to left speaker?). System is only 5 days old today so I'd prefer to find a work-around beyond manual balance biasing but will certainly be on the horn to the dealer if I can't find the cause and fix it within a day or two.
Statements in my posts are opinion only, not to be construed as fact. Any projects I engage in are at my own risk! Their outcome cannot be assured and may result in success, small/no change or catastrophic failure. I encourage no one rely on anything I say or do as gospel and to realize your mileage may vary!