Unable to send audio to Lenovo Smart Clock Essential

I’m using the say() command to send speech to Google Home devices in the home. This works fine for Google Home Nest Hub (with screen) that we have and a Sonos Beam, but doesn’t work for the 3x Lenovo Smart Clock Essential devices we have.

I’m using the Google TTS service and have tried a number of different voices. Eg.

  say("Just testing", "googletts:enAUNewsE", "chromecast:chromecast:bedside_3")

When the command runs, the device makes the “announcement chirp” which normally preceeds the voice message - but then nothing. For the same devices, I can stream audio from Spotify mobile apps so Chromecasting in general seems to work for those.

Is this a bug in OH? How can I start to debug this?