I’ve tried new batteries but to no effect. As I mentioned, the remote controls the Beam just fine after power-cycling the Beam, so it seems unlikely that interference is a possible cause.
As a software engineer, I suspect there’s an issue in the Beam’s software/firmware...perhaps the Beam maintains an internal log that may offer some clue…?
You will need the Sonos Support Staff to look at your system diagnostic report(s) - just post their references back here in the thread. If no one responds here in the next 24 hours, then you can contact the Support Staff via this LINK
The only other consideration is a factory reset, (if it’s not your only sonos product in the Household) but I would leave that as a very last resort.
Hope you get it sorted soon.