AirPlay 2 to Sonos Speakers Out of Phase

I all. I am having a major issue with AirPlay 2. I have tried a few times to diagnose with Sonos support but with no luck. Really hoping someone can help.

I have a home cinema set up in my lounge (PlayBase, Sub, 2 x Play 1’s), then various Sonos Ones around the house. 

When I AirPlay to multiple speakers around the house they keep dropping out of sync. However, if I AirPlay to one speaker, then group others to it in the Sonos app, then they stay in sync. I am using a Sonos Boost.

Any ideas or similar experiences?