There’s at least a couple of potential issues I can think of, but that is not exhaustive. I have a pair of PLAY:3s that are working without issue. Right now, they’re grouped with a Sonos One that is receiving an AirPlay 2 signal from my Apple TV.
You've not explained how these Sonos devices are connected to your LAN, it could be as simple as some form of wifi interference. or perhaps a duplicate IP address issue, causing one or more devices to ‘fight’ for access. Or, it (very unlikely, but not impossible) be an issue with the memory going bad in the Sonos devices.
Have you submitted a system diagnostic within 10 minutes of experiencing this problem, and called Sonos Support to discuss it?
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.
Yes, I have submitted diagnostics and spoken to Sonos Support. That resulted in some advice, like making a total reset of the players, to clear clogged memory. That did not help. I have not talked to Sonos Support since then. The waiting time for a call is quite prohibitive. See also the previous thread where I posted more details.
Wifi interference? Well, I moved my players around to different places in my flat (Again, see the previous thread.) Also, Wifi interference does not seem a likely explanation for a problem that goes away after plugging the players out and back to the electrical power and then comes back one-two week later. Rather such a problem would come and go, depending on the source for the disturbances.
All my Sonos devices have a fixed IP-address. The Sonos device that is connected to the LAN is my Port. Previously, it was exactly the Play 3 I had problems with that was connected to the LAN. Thinking that the poor device was being overloaded,my first troubleshooting step was to move the LAN connection to the Port.
While you seem to be lucky, several other Play3 owners have posted testimonials, and in some cases, they seem to have more problems than I have. (Again, refer to the original thread.)