Speakers keep grouping when not wanted

Slightly odd problem which started last week.

When asking a Sonos One/Beam to play something, it is automatically grouping together all other Alexa-enabled Sonos speakers to play it.

This is despite them not being grouped or other speakers even playing something else at the time.

Earlier today, with the Sonos app open, I asked the One in the kitchen to play Radio One and watched in the app as it lumped all the Alexa-enabled speakers together to play Radio One - even though they were already in use playing other things.

It doesn't seem to include the Play:1 in my set-up, though.

I have a Beam, two Sonos Ones (not paired together) and the Play:1.

If it helps, my diagnostic number is 1910432264.

Thanks in advance (and hope!).