I have exactly the same problem as the one described by another user, Mathias Pageau earlier, except that I am using X1 and Z1 controllers.
I experience audio drops, and cannot have a track being played correctly without being interrupted by these audio drops all over again.
I have been spending all day trying to move the buffer size and following the tips at https://support.native-instruments.com/hc/en-us/articles/210296445-Mac-Tuning-Tips-for-Audio-Processing but it would not solve the problem.
I did not have any problem like this using Traktor 2 which was perfectly stable.
I checked and it seems my Imac meets the system requirements for Traktor 3.
Intel Core i7 3,1 GHz | Mac Os 10,14,6 | Kontrol X1 Kontrol Z1 Native