Ah…is your ‘sud’ a Sub? Took me a minute to figure that out . Also, I’m assuming your ‘Sonos 3’ speakers are actually Sonos PLAY:3s.

I’m not certain why you’re getting your system disconnected, though. There are a couple of things I’d try, they may make a difference, if you can. First, I’d try connecting one of your regular speakers (not the Sub) to your router with an Ethernet cable. Give the system a couple of minutes to settle down before testing. It may be valuable to unplug, then plug back in your speakers, too.

I would also be tempted to set up reserved IP addresses for all your Sonos. Instruction on how to do so should be in the router’s manual, since they all seem to handle it in a slightly different manner. You can do an easy test to see if this might be an issue if you just unplug all your Sonos devices, and while they’re unplugged, reboot your router. Give the router a couple of minutes to reboot before plugging back in your Sonos.

Probably related to the Play:3 firmware issue (ongoing for months and related discussions found in the community) wouldn’t count on a fix given the situation, recommend downgrading to S1 or getting rid of the Sonos gear like I did while you can.

Unfortunately, the option to downgrade to S1 is not available with the new app.  It will sometime in the future

https://support.sonos.com/en-us/article/downgrade-a-sonos-product-to-s1

If you feel adventurous, you could go back to the old version of the s2 app.  Instructions for Android and IOS can be found here.

As far as I am aware (seen related posts here in the community) it is still possible to downgrade to S1 from the old S2 App if you are lucky enough to still have it or are able to obtain it.