How can it be a good user experience when every time I go back to the app it starts up on the home screen and not where I have left it before?

This is extremely annoying. If you've chosen an artist or album you have to go though all the screens and clicks again of you want to change to another album. If there are hundreds of artists or albums you scroll for a long time (another annoying"feature").

Even that bad that it some times doesn't even recognise or finds the current Sonos system.

This is the worst app in years of app development.

(Feel free to add your worst "feature".) 

Thanks (or maybe better no thanks for this "app", which more like a "no-app")

P.S. open your api so that more advanced and experienced developers can create somethin sensible and usable.