TTS guide?

I finally got the IKEA Symfonisk speaker and the TTS works great. (I now have audible notifications when someone comes to the door).

However, I have a strange issue, I wonder if anyone has come across?

The volume on the IKEA Symfonisk speaker increases by itself. I can turn the volume down (via the button) or set the volume via the Hubitat devices page, but randomly, after a while, the speaker increases to max volume.

Has anyone encountered this? Or have any suggestions to resolve?