I had issue with my s4/mk3 since May 2024. I still have guarantee. 
Im in a ticket loop and been trying everything support asked me for. And want to replace my unit. But just NI just want me to do more tests. Im a user since 16 years and work as a pro dj. 
So I have to cancel dj gigs, not so good. The problem is pitch faders and also that player stop without sound. 
I tested; 
Changed 3 pc, new usb, latency, installed demo, and so on, even tried a new controller and then it works! I have had pro it technichens that have veen looking thru everything. 
I sent my unit to NI but it returned and yesterday they mentioned that NI sent me a new unit but thats not True.
Almost 3 month now and NI just want more test, its not ok! I cant work !!
I think there is a curcuit on the board thats no good.
Answers from Pedro looks like ai answers. 
Please where can i get in contact with a manager or so? 
I tried info email, but support answer that too. 
Charlie in sweden.