You might be experiencing wireless interference. Try the troubleshooting tips in this article:

https://support.sonos.com/s/article/3286?language=en_US

Thank you @GuitarSuperstar. Sadly we do not have the option to change the channel with Eero. Appreciate your reply still. 

Are you able to wire any of your Sonos speakers (not a Sub or surround speaker) directly to your main router with an ethernet cable? This will create SonosNet, a separate mesh network for just your Sonos speakers that could improve your wireless performance including AirPlay.

When you’re using airplay,  are the homepods and Arc connected via airplay?  Or is it case where only the homepods are connected via airplay and the Arc is still getting audio through it’s wired connection to the TV?

I don’t have a need to send audio to HomePods and Arc simultaneously. However, the setup below causes no out of sync issues. This assumes your primary connections to TV are are follows:

1. Arc to HDMI ARC or eARC Port on TV
2. AppleTV to available HDMI Port

NEXT

1. Go to AppleTV Settings > AirPlay and HomeKit > Airplay ON > Allow Access > Anuone on the Same Network > Conference Roon Display OFF > AirPlay Display Underscan AUTO > HomeKit  Room > Select Room with Arc > Home Hub > My Home CONNECTED
2. Go to AppleTV Settings > Vide and Audio > Audio Output > Default Audio Output RECEIVER SPEAKERS > Temporary Audio Output > Select Receiver Speakers and Home Pod Rooms
3. To stop sending audio to HomePods deselect Temporary Audio Output speakers

Note: AppleTV remote will control volume for Arc. HomePod volume will have to be adjusted via HomePod direct. 

Only the HomePods are connected via AirPlay and the Arc is getting audio from the wired connection.

Well, you could get lucky but the audio paths to the Arc and to the HomePods are totally different. Different processing requirements; different latency variation; different buffering strategies. One shouldn’t expect sync at all.