Problems with iPhone App

I’m truly sorry you’re having such a bad experience. What did Sonos support say when you submitted a diagnostic, and called them?

I, too am a long time user of Sonos, with over 20 devices in my ‘home’, and a couple of dozen more spread across two other ‘homes’ that I support. 

Based on what you’ve posted, since I don’t have access to any hard data like Sonos would, I would diagnose network issues, most likely dueling IP addresses, which would cause all of the issues you’ve put in your post, but not issues caused by the app. This is a semi-common occurrence due to the fact that when there is a Sonos software update, the devices reboot, and ask for a new IP from the router. If the router has ‘forgotten’ (Power surge? Some other failure?) what it has handed out, it can easily give IP addresses that are already in use. 

As a test, I’d start with a network refresh, by unplugging all Sonos devices from power, then rebooting your router. Once the router has had a couple of minutes to come back up, I’d power back on the Sonos devices.

But ultimately, this is a guess, based merely on my experience in helping others on this forum. Your best bet remains to contact Sonos support directly, and provide them hard data which will help them figure out why your experience is so troubled.