Youtube video stutters when Airplayed from Safari MacOS to Apple TV

I'm not sure whether this problem (which has been happening for a couple of months) has been caused by the latest Mojave update or by the latest tvOS.

When I Airplay a youtube video from Safari on Mac to Apple TV the video and audio on the TV stutters continuously and the video cannot be watched. When I stop the clip from playing on the Mac, the clip keeps playing on the Apple TV.

I'm on an all Apple network (Time Capsule approx 3 metres from the Mac) and a couple of Airport Express units in other parts of the house. I don't have any Bluetooth peripherals such as a Wonderboom that I have seen cause problems on other Apple TVs. All software is up to date.

Any ideas most appreciated.