Safari on MacBook — cannot play sound on HomePods

M1 MacBook, current on OS updates

HomePod stereo pair

Up until a few days ago, I could watch video on Safari and select my HomePods as the output source. Suddenly that changed: I can select the HomePods as my output source, but when I start the video in Safari the sound plays on the HomePods for about a second, then reverts back to my MacBook speakers. I’ve tried this repeatedly and that is now the ways it seems to “work”.

Any ideas out there?