Remove/unbond the surround speakers from the Arc in the Sonos app and unplug the Arc and surround speakers from power for a couple of minutes. Reboot your router. Then plug the speakers back in and add/bond the surrounds back to the Arc.

Still something wrong… the skipping got less frequent and takes less time to recover but isn’t completely gone, and it also keeps going out of sync in waves.

You could be experiencing wireless interference. Try some of the troubleshooting tips in this article:

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

If possible, you might also try wiring one Sonos speaker (not a Sub or surround) directly to the router with an ethernet cable.

Are you allowing the surround speakers to connect via their radio (essentially wifi)  to the Arc, i.e. having the wireless radio turned on on all three devices? Or are you trying a wired setup with the wifi turned off on all of them?

The Arc itself is connected by cable and wifi disabled (because of issues with a nearby AP causing interference), the One SL’s and the Sub are wireless. I also have a Boost installed because of prior network issues.

Let me try to activate the wireless option on the Arc again...

I suspect that’s your ‘issue’. Normally the surrounds and sub connect wirelessly to the soundbar. Turning off the WiFi in the soundbar forces them to go an odd path through your router and BOOST. That ‘odd’ path is likely causing the de sync issue you’re experiencing.

Sonos, during the set up of surrounds and Subs, doesn’t really tell you that the devices are changing from your router or BOOST’s signal in a normal room configuration to a wireless signal created by your soundbar when used in a ‘home theater’ context.

Seems to be resolved by re-enabling the wifi on the ARC.

Thx