RFID check

All works good, but after few hours, arduino needs a reset because it don't read anymore..
RFID reader's led blink, but door didn't open (arduino don't send any signal to relay)

I don't know why, but...

#define txPin 11
#define rxPin 10

SoftwareSerial RFID(rxPin, txPin);

You've told the SoftwareSerial instance the these pins are its to use, and yet

  pinMode(txPin, OUTPUT); 
  pinMode(rxPin, INPUT);

You're diddling with them. Why?

  pinMode(6,OUTPUT);
  pinMode(12,OUTPUT);

How come all the pins don't get meaningful names?

byte tag1[4] = {0xAA,0xBB,0xCC,0xDD};
byte tag2[4] = {0xAE,0xBE,0xCE,0xDE};
boolean tag1_card = false;

Two tags, numbered; one boolean, also numbered. Why is the boolean numbered?

    for (int i=0; i<4; i++)
      if(memcmp(data,tag1,4)==0) tag1_card = true;
      else if(memcmp(data,tag2,4)==0) tag1_card = true;

A lot of curly braces missing here...