CONNECT lagging/out of sync/echoing

I update the S2 app on my phone (and the software running on all my speakers) to 14.18 following an in-app prompt a few days ago.

Since then my Connect has been gradually starting to lose time (lag) behind all the other speakers, getting continually further behind.  The echo caused by the lag becomes noticeable after a few hours, and after 24 hours I’d say it’s more than half a second behind.  The lag can be eliminated by rebooting the Connect, ungrouping it from my other speakers, or switching to a line-in source, but it soon returns and appears to get progressively worse.

I’ve spent (wasted) a couple of hours talking to Sonos support through live chat and on the phone with no success.  As usual they have run through their standard set of responses, for example “there’s a lot of wireless interference”.  Well yes, I live in a thick-walled house, in a built-up area, of a densely populated country, not a log cabin made of balsa wood in the middle of nowhere.  Of course there’s a lot of interference.  There was a lot of interference last week too before this issue appeared.  They’ve had me jump through their usual hoops - rebooting all the speakers in turn, restarting my router, switching to a different wireless channel.  Of course none of the solutions worked.  Frankly they are just clutching at straws.

I'm no network engineer but I don’t believe wireless interference can cause speakers to fall out of sync, and even if it did then that would constitute a fault with the system design.  It seems pretty obvious to me that there’s a software bug in the most recent update which has caused this issue.  So if you are also experiencing it (as are a couple of other people on this forum), you aren’t imagining things.

I’ll keep ringing Sonos every morning until this issue is resolved, which from their responses so far could be a while.  Their last word to me today was “I will write your case here so our engineers will take a look and see if the issue is with the software. If it is an issue with the software it should be solved with the new updates :)“  My response was that it will only be solved if the issue is acknowledged and actively investigated.  Simply saying it will be resolved in future updates doesn't make sense and frankly isn't really good enough.