It’s also possible that each app may have its own audio settings.
Technically, when using the HDMI-ARC connection, the client (the Sonos) is supposed to be dictating to the hub (the TV) what kind of signal the hub is supposed to be allowed to send. I would look at two things for this issue. First, make sure that the TV has HDMI-CEC turned on. HDMI-ARC is a subset of that, if it’s turned off, the system won’t be communicating properly. Second, and less obvious, is I would try a full reboot of the TV, by first checking for any updates to the software from Sony, and then unplugging it from the wall for two minutes before plugging it back in. This forces a refresh of the TV’s OS, and should help if there was an issue that wouldn’t else wise be cleared.