Naim Uniti sound issues on headphones and on mute?

Hello

Long time lurker (great forum) and Uniti owner (early unit). My first post here and I have searched the forum first. Be patient please 

I wondered if my issue is general or specific to me and therefore fixable and worth the trip to dealer, no device for weeks etc.

When using UPnP (wired) and listening on headphones I hear very distinct clicking ahead of the track starting and throughout it playing. The noise is also there when listening via speakers if turned up loud and my ear is placed close to the speaker but on headphones it so noticeable as to make them unusable. This doesn't happen on any other input. Changed listening habits has forced me to try using headphones. 

I'm assuming it is crossover from the network card or some other circuit. Anyone else got this issue?

A second noise isolation issue I've noticed is that when on DAB input, and mute is on, the audio is still there but at much reduced volume through the speakers.  This doesn't happen on other inputs.  I leave mute on when not using the unit.

Again, anyone else experience this?

Maybe it is just time for the inevitable upgrade for me to add headphone listening to my list.

Thanks.