I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. The diagnostic should contain information about both what is causing the volume to be raised, and the dot, dot, dot sound.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.
My guess would be something wrong with the OS, and it’s reading errant pressure on the controller. It might be interesting to close the controller before it reaches top volume, if that’s possible, and see if it still continues.
The other thing I’d double check is the capacitive buttons on the top of the device. Make sure it’s clean, and try turning them off from inside the Sonos controller.
