Gradual Sonos volume reduction

In Home Assistant I was able to send volume down commands, seperated by delays to create a nice smooth sounding fade out.

How can I achieve this with HE?

It appears that when you click Volume Down in the device UI, the volume decreases, but if you call "Lower volume" from Rule Machine, it does not work.

Anyone? File a bug with support?

Ah, found some errors:

app:1342019-06-16 14:45:44.296 errorjava.lang.IllegalArgumentException: Command 'currentValue' is not supported by device. (appButtonHandler)

app:1342019-06-16 14:45:44.268 infoAction: Bathroom Sonos: Lower volume