lagging

If you explore this community you will find this is a common issue.

Fixing the IP addresses for your speakers could help, it has for others.

But be patient and things will work even if it is slow. If things persist try restarting the speakers and your router, if that does not help then call Sonos support.

Merry Christmas.

Maybe?

https://support.sonos.com/en-us/article/improve-your-sonos-products-wifi-connection

Thanks for your suggestion, but My Wi-Fi signal is strong.
The Spotify app works perfect with my Marantz speaker system

only had trouble with the SONOS system

It isn’t about your Wi-Fi it is about how happy your Sonos are with your Wi-Fi and the overall Radio Frequency environment.

My Wi-Fi is beyond excellent… Sonos still had connection issues.

The FAQ helped greatly and solved a couple problems.

Unsolved ones required a call to Sonos Support, that ended up pointing out I’d missed things in the FAQ that weren’t real obvious (to me) but were still causing issues. Not a single change needed to my Wi-Fi but it all came down to Wi-Fi issues in the end.

If you are sure you don’t have a problem that can be fixed on your end, then submitting a diagnostic and calling Sonos support is your best option.

I have the same issues as the OP - the app says my signal strength is “Strong” and yet the response is still horribly laggy where before the app updates it was perfectly fine.  For example, if I press the volume control on my speakers it can take many seconds for anything to happen to the volume.  This used to be instantaneous, as you’d expect from expensive audio hardware.

It also now takes a long time for music that I’ve requested by the app to start playing on the speakers, when again it used to be much faster.  From what I’ve read on these forums this is because all the commands are now being sent via the WAN and back to my speakers, rather than directly.

If I didn’t have a house full of these speakers I would 100% be replacing them with something that worked well.

I’ve got four speakers. I would do the same too.

What was it you had to change?

Removed an electronic device that did not have a radio but was still spewing RF noise.

Like when I ‘retired’ a microwave that was, while it was running, causing issues for my kitchen speakers. That took way too long to track down, which seems dumb in retrospect, as the issue was only on the rare occasions the microwave was running. As soon as I replaced it with a newer one, the issue disappeared. 

I would try to reserve IP for Sonos.
Now I don't know which Sonos speakers you have but you can try, it worked for me and mine works pretty much flawlessly.

Arc Ultra and reserved IP/5Ghz Wifi.