Thanks, the devices are all on ethernet and have been in their existing locations for quite some time and it's been very stable for some years.
As the Apple TV is quite close to the projector an audio extraction device would probably be less impractical due to need to run long cables, though not impossible. May be worth exploring if things don't settle down - I'd actually wondered in the past when Airplay often introduced lip sync issues but these days it's much better.
The hi-fi component recently has a firmware update too, so it's possible that could be the issue. It has RCA/optical/SPDIF inputs as well as Airplay, Chromecast etc. It has HDMI ARC but the projector doesn't support that.
I've long been planning to reinstate an old Panasonic AV amp with 4k HDMI passthrough so could potentially use that to feed video to projector and audio to hi-fi, but it would involve finding space for the extra component, though perhaps I should try as it could act as a switch for gaming consoles and BluRay players.
The recent AppleTV update seems to have brought an odd feature of adding close captions to rewinded content which then turn off - I guess this might be to help you navigate visually when rewinding, but I do wonder if adding this feature something else in the audio output pipeline might have changed.
A few years ago I tried a pair of original HomePods configured to stereo and the sound was actually pretty good however in their case wi-fi was definitely a limiting factor (last gen 3TB Time Capsule and AirPort Express), a real shame Apple stopped making networking hardware as it was so simple to configure.
