Installed the new Apple TV 4K along with its new Siri remote. AppleTV feeds Onkyo receiver which feeds TV. Home theater control on AppleTv is on with volume control set to Auto via HFMI (receiver). Channels app audio driver is set to experimental to prevent audio stutter when using the remote to issue Siri commands.
The new remote has a dedicated mute button. When clicking MUTE it works perfectly in Channels, no sound.
When I click it again to un-MUTE, most times it pauses live broadcast momentarily, and maybe 2 or more seconds it will either fail to un-MUTE or successfully un-MUTE, seems random whether it responds correctly or not. When it refuses to un-MUTE, hitting up volume restores audio ... limited use in other apps, this new remote’s mute button works just fine, when muting and un-muting.