CDJ2000 restarts by it self

Hello, I am using two cdj's 2000 and in the last 3 weeks as I was in the club playing music , the one cdj restarted as it was playing without touching anything more than 5 times. I am using sd cards and usb ,not laptop . I have update the firmware to the latest version. What might be the problem. I must notice that I had the same problem in two clubs, so I don't think that is problem with electricity. Thank you.