Beam + One SL, surround sound doesn't work over ethernet

Hello, here is my setup:

x1 Beam over Wifi

x2 One SL over Wifi + Ethernet

I want my One SLs to only use Ethernet.

Last week, I did put my One SLs over Ethernet and disabled Wi-Fi from both of them with the SONOS app. Since then, the surround sound stopped working (it is not a TV problem, I tested with a few SONOS radio stations). 

It’s only the surround that doesn’t work though, because I can still use the controls on them, increasing/decreasing volume etc, it controls the whole setup. On the app they are not displaying any error. Also, sometimes the status light stays green. I read that it means it is muted but increasing the volume from the app itself or from any of the One SL doesn’t change anything.

I tried, turning them off and on a few times. I also removed them from the app and did re-set them up. Nothing works, except when I turn the Wifi back on, everything goes back to normal.

Didn’t find a similar problem over the internet. What could be the problem?

Thank you,

Loris.