Naim Uniti Nova problems after firmware upgrade

[Similar message posted in the Naim Community forums]

I don’t think I posted a query about my initial problem here so I better start at the beginning. I should say that although I can’t believe the firmware has much to do with the problem, until I did the upgrade the Uniti Nova was working flawlessly.

Back in early April the Naim app prompted me that a firmware upgrade was available went ahead with the upgrade. The Nova disappeared from the app and by the time I went to bed an hour later it was still not back. The next morning it was still gone so I pressed the front standby button to wake it up and the Nova soon started emitting loud, slow, high pitched pulsing noises and I had to unplug the speakers. I then managed to have the unit on long enough to be recognized by the app. I looked at the firmware on the app which said it was up to date. Plugging the speakers back on and powering up the Nova just resulted the same problem. After I did a factory reset there was also a crackling sound from inside the Nova enclosure which sounded like sparks we going off and a faint burning smell.

Since then the Nova has been back to Focal Naim for repair and last evening I received it back after repair. However now, after connecting the speakers and powering up, when I try and play something I get a thin, tinny sound at low volume and turning the volume up just makes the same tinny/scratchy sound det irritatingly louder.

I have done a factory reset but that didn’t help. Am I missing something that I need to do or does it need to go back for repairs? I hope not - it cost a lot to ship it back and worse, it meant a long wait before I got it back. Any thoughts or suggestions would be welcome.