Ah, a CR200/Control. I’m afraid they’re notorious for touchscreen failures as they age. When this strikes a small region of the screen stops responding. As time progresses the malaise can spread.
I’m afraid there’s no cure, though feel free to contact Sonos phone support if you wish.
If you have an old smartphone which can be re-purposed as a Sonos controller all well and good, otherwise the simplest solution is to replace the CR200 with a cheap tablet such as an Amazon Fire. As a bonus you’d end up with a much more functional controller app.