So, I can use an OLD Akai LPD 8 to control Traktor Pro 2, but not an old Kontrol X1... Isn't this a MIDI-controller as well?
I'd see if Controller Editor recognizes the X1. Just to be sure it works at all.
@Ben Kinx Have you tried with Controller Editor 2.1.0?
Compatibility of Native Instruments Products on macOS