Yes I have tried that... but I don’t won’t to discuss FLAC. For me it’s not an option. AIFF works fine for me with excellent sound on all my systems: Pioneer DJ, Mac, etc. even with the core and Nova except in HighRes. And this have to be a bug, because the specs says “Plays all”.
Sure you should be able to use whichever format is supported and you fancy to use! Still, you could try to download a .wav file or a .flac file, encode it as .aiff and give it a try. This would tell you whether the issue that you are experiencing is a Naim issue or a Qobuz issue. In the latter case good luck: I have sent to Qobuz a number of issue reports and never got any feedback from them: a miserable technical service. If it turns out to be a Naim issue, it will likely be sorted out with a firmware upgrade. In the meanwhile you could download .flac files and then batch convert to .aiff once the issue has been fixed.
I too have had miserable experiences with the 'technical' support from Qobuz, and the download experience, to the point that I will only buy from them if it cannot be got elsewhere. However, there is one advantage in that you can download your purchase as often as you like, and in different formats, offering CSOMMER a temporary solution to his current problem.
Very strange, because my experiences with Qobuz support have been very different. Qobuz support has been very quick to respond and resolve any issues I have had with downloads. I recall one instance where I had downloaded a dozen or so albums and had a problem with one specific track on one of the albums. They responded very quickly to my query, indicated that the issue appeared to be with their file of that track and so couldn't be quickly resolved. They invited me to download any alternative album at no cost. Can't get much better than that!
I haven't bought anything from them for a few months now, so I guess things might have changed, but I certainly have no complaints.