@Andrew > Welcome to the forums. :)
Firstly, the warranty will only be valid with your receipt and within the country of original purchase, which from what I read, I think you purchased them from within your country?
Second, it would be best to contact Technical Support for your region on the right side of this page. Explain to them you would like the product repaired as it is under warranty and they will direct you to your nearest Authorized Pioneer Repair Center. You will either take or send your HDJ's to them for repair. When contacting the Repair Center, ensure you tell them you would like them to fix it regardless because it's under warranty. If they continue to do the same thing, just call Tech Support back and explain the situation as they will be able to assist you best.
If nothing seems to work, come back to this thread and mention what happened; we'll see if Gavin or Pulse will be able to help out.
Best of luck. :)