<!-- language-all: lang-C++ -->

    void loop() { 
      Serial.println("NEW-------------");
      int x;
      int y[100];
      for(int i = 0; i<100; i++){ 
        x=RX.read(); 
        y[i] = x;
      } 
    ...
    }

You are reading data without checking if there is any data there. That's like watching the TV without checking if it is turned on. Of course you get weird data.

---

    SoftwareSerial RX(0,1); //(rx pin, tx pin)

Pins 0 and 1 are used by HardwareSerial. Why are you using them for SoftwareSerial?

---

    SoftwareSerial RX(0,1); //(rx pin, tx pin)
    ...

      Serial.begin(9600); 
      RX.begin(1200); 

So you initialized HardwareSerial, which now controls pins 0 and 1.

Then you try to initialize SoftwareSerial on those **same** pins! Would you mind explaining why?

Whatever your explanation is, it won't work.