Is your product under warranty?  Did Sonos offer you a discount on a replacement?

No, I have not heard of any lawsuit regarding the quality of Sonos 5 Gen 2 hardware, nor I have seen a high volume of complaints in this regard. 

The product is out of warranty and support offered 30% discount voucher on a new product once i return my £550 speaker to them. Seems like Sonos dont offer any repair service. I see hundreds of posts about this same fault so i think a class action legal case seems good if we can get some people together. 

Start by hiring a lawyer.

Don’t hire one and join the hundreds of folks here threatening legal action but doing nothing.

End of my legal advise and expertise.

Understood. There does seem to be a lots of cases on several forums of the same issue. I have done some more research here and contacted a Sonos repair company. I also found a thread where Sonos used to send replacements even for out of warranty situations like this one (linked). I also see a fixit site that does a teardown. Looks like the network board could be replaced. Does Sonos provide parts for self repair?

No, SONOS does not provide parts or repair services. 

Knowing this, have you contacted Sonos support by phone and had them diagnose your speaker to see if it has the same issue?

Instead of planing a lawsuit (which may never happen) get in contact with support, allow them to diagnose the issue and see what they decide to do if it in fact a hardware fault in the speaker

Or don’t, and start a class action suit.

Thanks for message.

Yes - Sonos support ran the diagnostics and it is a dead wifi board - hence i would like to see if i can get a replacement board rather than send a huge speaker back to be scrapped. Seems like a good case for the new “Right to repair”

You can repair it with no complaints from Sonos. Also with no help from Sonos.

Ebay and the like have a good number of “parts-only” Sonos that if you shop carefully should yield  good WiFi board.

As an alternative you could try to identify the board and buy an exact replacement for it. Even a small difference may cause conflicts with the driver Sonos has loaded in the speaker.

There are 3rd-party Sonos repairers who advertise online near to where I reside in the UK - I’ve not ever used them however, so cannot make any recommendations, but it maybe worth researching these things online.

Just discovered this myself whilst trying to downgrade from the disaster that is S2 - which you cannot do unless the S2 app can connect to the speaker via WiFi, there’s no way to downgrade whilst the speaker it it’s connected via Ethernet. 

So… one of my stereo pair of Play:5 Gen2’s is now on S1 and the other is stuck on the green pulsing light and can’t be downgraded.

So I either have to put up with S2 being DOA, or a dead speaker - these Play:5’s do seem to be dropping like flies from some google searches. This one at least I can cable in, the other in this pair can’t be easily.

Support offered me a 30% off code off a new product, at this stage with 3 execs departing in a week and the S2 shambles, I don’t have the trust of confidence in Sonos to make further investments with them. 

Have you thought about any repair options on the Play:5 that might be useful to share?