Alexa keeps ungrouping my rooms :(

I am using 4 Sonos One in different rooms of my appartment and everything worked flawlessly with Alexa until a few weeks ago. I used to be able to tell Alexa to "play radio in the kitchen" and it would start playing my last tune-in station in the kitchen AND all the rooms in the same group. When I use the same command now, Alexa ungroups all my Sonos players and starts playing that radio station only in the kitchen.

After doing some reading on how to resolve the issue, I created a group within the Alexa app, which I called "Sonos" and tried the command "play radio on Sonos". This does actually prompt her to play radio on all 4 speakers, but she first asks me "what would you like to hear?". No matter what I answer, she always just seems to pick an arbitrary radio station from tune-in and start playing that one. I must have tried dozens of times, but there is no way she'd start playing the one tune-in station I want her to play on my 4 speakers... which has never been a problem before.

Any suggestions?