@hififish I am having the exact same issue as you with my supernait. When I use the remote, both mute buttons light up and I get clicking in my speakers. Interestingly it started with every button on the Naim remote, now just seems to be volume control after a reset.
Did you ever resolve your issue? Almost like the motor in the volume control is causing something to happen.
Apologies for the late reply, I was holding off responding as I had an inkling of what may be the problem here, but had never seen it manifest itself by firing remote commands - until today!
There is a known issue with the original Supernait where a capacitor in the brown-out detect circuit fails & causes the symptoms you describe. Previously, I had only seen a permanent fault state, but this customer’s unit was behaving exactly as yours is - fire a command, then mute state. Leave it a while, then ok until another IR command.
So I would recommend having the unit serviced, at Naim we replace the (electrolytic) capacitor with a tantalum one on every unit returned, whether serviced or not, for preventative maintenance.
The brown-out detect circuit monitors the incoming AC power for transient dropouts & strives to mute the audio output before any possible nastyness can shock a listener or worse, cause speaker damage.