HomePod (2nd generation) unexpectedly blasts music at 100% volume

I have a HomePod (2nd generation) in the living room. I see it to play soft music overnight for my dogs, volume 11%. Last night, at 3:30 a.m., the HomePod starts blasting music at 100%. I use the HomePod mini in my bedroom to reset the volume. Night’s sleep: gone.

The same thing happened again at around 6 a.m. This happened once before, a couple of months ago. Does anyone know what’s going on? I’m not going to bother calling Apple Support because they won’t know.