After a few settings in my router, I now have a much better experience with the Sonos App. Playing music and adjusting the volume is done almost without delays and the App opens/loads significantly faster.

I'll try to make it short :)
I have a Wifi 6 router that provides a very strong and stable wifi network, so I should therefore get a fairly high speed on the products that support Wifi 6. I discovered that my Arc Ultra was on 2.4Ghz even though it supports 5Ghz on Wifi 6.

I turned off my Sub and 2xEra300 so that only Ultra was on, restarted my Ultra and saw that it was connected to 5Ghz. After that I went into my router where I initially discovered that it was not set to the highest Mhz on the 2.4 & 5Ghz network. Switched to the highest Mhz, and I locked the iP Ultra was connected to.

Turned off Ultra and restarted my router and Ultra, could see that Ultra connected to the locked IP and on 5Ghz. Then I turned on my Sub and 2xEra300. After a very short time I could see everything was connected correctly in my Sonos App.

I have now tested it for a week where I have restarted devices and the router several times to make sure it runs on the same IP and 5Ghz. My experience is an extremely stable system. The app opens/loads significantly faster and has virtually no delays in playing music and adjusting the sound. I have an iPhone 15Pro that is also connected to 5Ghz, my thoughts are that the device that has installed the App should preferably be on the same frequency as Sonos and preferably 5Ghz.

I think this will also improve the experience if you lock your 2.4Ghz if you do not have the opportunity to achieve 5Ghz. At least try it because I have had a whole new experience with the Sonos system.