Problem with Pioneer DJM S9 sounding distorted

Sorry for the delayed response.  Have you got this sorted?

I also have the same problem. Could my mixer be defected?

I had the same problem recently.  I am using a DJM 909, SL4, 2017 Mac Book Pro.  After I restarted the computer it was fine.  Luckily it happened at the end of a 4 hour shift.  I did notice I was connected to the wifi (well, the wifi was on but not connected to the internet), normally I always have the wifi off.    

No credible answers for this dilemma with many of Pioneer's pro audio equipment. Let me enlighten many of you since Pioneer doesn't seem to have a clue. I am a 34 year master electronics technician here in Michigan servicing majority of Detroit's DJs gig rigs for same amount of time. What Im noticing is that either fuses, resistors and/or faulty DSP on the mainboard for the DDJ-S9 is the culprit for distorted audio output at higher volumes. Main boards need replacing according to Pioneer's service manual and their support team. Pioneer also suggests that techs should not attempt a repair on the main assembly board although I have many times and have replaced faulty components to save Detroit DJs from shelling out unnecessary gig funds for a repair that's bound to happen again and again. My suggestion is to NEVER plug anything into any Pioneer products inputs or outputs that has current flowing such as powered speakers and amps that are active. Until Pioneer Tokyo can send me DSP chips most of you all will be replacing this main board @ $432 plus your tech's wages.