iPhone iOS18 TV remote app : app stops controlling volume on Apple TV, will only adjust ringer volume

iPhone 15 Pro, iOS18

Apple TV 4K Gen2, TVOS18

Until iOS18, the remote app worked flawlessly when watching content on our Apple TV. Now, after the update, the volume control button works as before *sometimes*, then suddenly it will only control the phone’s ringer volume. Anyone else seeing this, or have a solution? I’ve reported the bug but this group is frequently faster with a fix.