If you can confirm your actually getting the hi rez files from Tidal, then i'd ask mac's service department.
I had a similar problem with the ARC input on the digital 2 board in my C2700 and it turned out to be the gain was set to hi for the digital input. MAC's service department answered me the next day and gave me the procedure to change the gain setting and its works flawlessly now.
I'm not saying your problem is the same as mine, but MAC's service personnel seem to answer fast so worth asking them after you confirm you're getting the hi rez files from tidal. double check your tidal settings potentially after an update they were reset.