This is the first time I’ve heard of this being an issue with Pandora. Since they’re out in the lanai, any chance there might be an animal jumping on them, triggering the ‘play’ and volume? There have been some reports that suggest sometimes those buttons are sensitive enough to be triggered by dust ( and I’d assume some extra nudging, but the issue went away when the device was wiped down). I’d be tempted to do two things. First, go in to the room settings in the controller, and turn off the extra hard buttons. Then, if it still happens, submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.
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.