I found disconnecting it and taking it for a drive in the car - ie to the Meridian factory. When you get it there it will be working and you feel really stupid for having a problem that is suddenly fixed the moment the Meridian guys take a look at it.

Meridian owner since 1992
Prime & PSU, Focal Elear headphones, Roon (ROCK 8Gi5 NUC), Explorer 1 & 2, F80. 200/203, various Sonos (via Roon).