HomePod mini connectivity in stereo

Both speakers play music independently, not the same track, often tracks I haven't selected from those stored on my iPhone 13 pro max.

On setting up both speakers I chose one to be the right hand speaker but wasn't asked if the other should be the left speaker.

Neither speaker appears in the list of bluetooth devices on my iPhone but there is a Bose Revolve+ device listed.

I've contacted the company who supplies my broadband and they tell me that their supplied home router from which my home wifi is connected is not the problem.

As I compose this question music suddenly played in stereo but it was intermittent, but on moving around various sections of my iMac the stereo cut out.

Tried to use Airplay but that I all problematical.