Details are here:

I don’t think they will hit the dates though.

Hi there.  Since the day you updated the Sonos App, the app is not working properly.  It's very slow when it opens, and many times it doesn't work, it can't open and I have to delete the app from my phone, then download it again and it causes problems again.  Put the old app back and it was 1000 times better.  Why do something when it wasn't necessary. New Sonos App is rubbish.

I think that it’s is incredibly naive of Sonos to be launching a line of headphones when they still have a suboptimal app out there and so many people complaining. I for one would not even consider another purchase until this outstanding series of issues are solved. 

They have a suboptimal app precisely because they were launching their headphones.