Problems with a "Arduino Compatible Analogue Joystick Controller [PC]"

I recently bought the following on amazon: http://www.amazon.co.uk/gp/product/B00DB76XIM?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00

But it's not behaving as expected. I was anticipating it being simply two potentiometers, one for X and one for Y, and that the two pins Vx and Vy would read the voltages across these potentiometers, however when I ran the following simple sketch:

const int XRpin = A0;
const int YPpin = A1;
void setup() {
  Serial.begin(9600); 
}

void loop() {
  int XRval = analogRead(XRpin);
  int YPval = analogRead(YPval);
  Serial.print("X or Roll value: ");
  Serial.print(XRval);
  Serial.print("\n");
  delay(1000);
  Serial.print("Y or Pitch value: ");
  Serial.print(YPval);
  Serial.print("\n");
  Serial.print("\n");
  delay(2000);
}

The two voltages being read were always the same. My circuit was simply the +5V and GND pins wired into the arduino's respective pins and the Vx and Vy into analog inputs 0 and 1. Any idea why this behaviour could be happening? Am I missing something obvious or is my unit probably just broken?

Check the circuit traces on the joystick board as some of the Chinese devices are not marked correctly.

To check your code and the ADC, replace both joystick inputs with 2:1 voltage dividers and see if you get around 512 for each channel.