I too have had huge problem with recording via X32Rack at 48Khz. 32 tracks that all sounded like line level sources recordedinto mic inputs i.e. sounding horribly overmodded.
Trying to reproduce the problem resulted in some recordings OK, some with clicks, some with crackling. But as with everyone else here, 44.1kHz recording is fine. Also no problems at all in two years of using uTrack X32 in full X32 desk at 48kHz.
I reckon these are all slightly different manifestations of the same (clocking?) problem when using the card in X32 Rack at 48kHz.
Would anyone from Cymatic like to update us please….?