Tidal was flat when I first tried it. But 6 weeks down the line and it sounds extremely good. For me, I guess it was the 272 burning in.
Indeed, Tidal is FLAC which can sound less than ideal on Naim, and the internet route and server latency at a particular time and or track replay can affect how hard the network tcp machine in the streamer works. In experiments I have undertaken I have found this can subtly affect SQ, although this is lessened to a fair degree by using an off board DAC from the streamer transport.