Mu-so QB no sound when using Spotify Connect

Hi. I have a Mu-so QB that I have been streaming Spotify through for a while. A few weeks ago it stopped audio. It is connecting correctly through Spotify Connect (as in the green pairing is done) and it appears to be playing a track but there is no sound. I’ve checked the obvious and it isn’t volume off, or Spotify device silent. What I have then done is reset the QB and re-pair on the network and then it works perfectly again, doing nothing different to when the sound stopped. But then after a couple of days (nothing obvious I can see I have done to make it drop the sound) the sound quits again.

This has happened many times and it is really frustrating.

If anyone has any ideas I’d love to hear. If there is any specific detail you need please let me know.

Big thanks.

Neil