Yet again more audio issues.

So I had problems with my DDJ-SX2 upon opening the box with no audio coming from the decks. After installing and re-installing the drivers/firmware i gave up and switched it all off for the night. Came back to it in the morning and without changing any volume dials or levers it worked by itself. It's now been less than a week and the audio again is not coming out of the DDJ-SX2. I paid £810 for this piece of kit and I expect it to work.