What is your router? Sounds like it might be iffy, try connecting one Sonos device via Ethernet to switch to SonosNet instead of wifi.

I’d start by setting static/reserved IP addresses for all your Sonos using your router’s DHCP page. It is fairly simple for most and should have a help screen or manual page for more help.

Power down all Sonos, reboot the router and power the Sonos back up.

If it happens after that look into WiFi issues.

I have a Ubiquiti UniFi router with two UniFi Access Points.  it is not really possible in my home to connect speakers to Ethernet. 
But, thanks for the tip. I can try this for a week or what with a temp cable. 

Good tip. Will try that a see if that resolves the issue. But… it worked like this the last 2 years without issues. 

Perhaps see if this link might assist you to resolve the mentioned issue…

https://github.com/IngmarStein/unifi-sonos-doc

Oh man its a Unifi network, well that makes a huge difference. Good luck to the OP.

I have no issues with my Unifi gear and Sonos… Because I wired one of my Sonos and do not try to connect any of them to my WiFi. Before I wired that one I had a wired Boost that worked well.

Kinda sucks because I really want a pair of 100s but can’t wire them, they won’t hook to SonosNet and I really do not want to open that can of Unifi worms again.

I did bookmark the doc link above though, just in case.

Perhaps not quite so much with the Era-100’s, but I suspect if you were to listen to a stereo pair of Era-300’s and how they sound, when playing Atmos music, I reckon you might make the leap to run all on your Unifi wireless signal. I personally think those slightly larger 300 speakers sound great. Their shape takes a little getting used to around the Home, but IMHO the Sonos engineers have excelled with that medium-sized speaker.

I’m now running my own system on a (plume) WiFi mesh setup here at Home and have recently handed my Sonos Boost to the Son-in-law. All seems to be working well in wireless mode. I understand the Unifi instructions in the link I posted, work well with Sonos too. If you do ever decide to switch away from SonosNet, then perhaps let us know if it goes well, or if any difficulties were encountered. Of course you could try the switch before purchasing anything, perhaps?

I do personally suspect (just a guess) that all new Sonos products, going forward, will likely be geared more towards wireless mode anyway, with no option to use SonosNet, as currently seen with the Era-100/300 products.

Home WiFi coverage and speed are improving all the time and with Sonos products now using the 5Ghz WiFi band, things have certainly improved. I am seeing faster device discovery times and ‘rooms’ are noticeably quicker to group/ungroup etc.

I can’t easily switch away from SonosNet as I have a number of my Sonos wired to Ethernet and as some of them are Beams and an Arc turning off the radios to remove the SonosNet isn’t an option. As I see it I can’t really test using the Ubiquity WiFi option without buying a pair of 100 or 300 speakers.

I don’t have a good spot for the 300s and the known painless option of more One SLs versus possible issues with the 100s has me putting off making a choice until I really need something.

Since I’m also looking at replacing my older Ubiquity Access Points with the latest generation ones I’m leaving the new generation Sonos speaker purchases on hold so I only have to fight this battle once.