I created an integer-array shuffling program in C but... but it seems to repeat a certain number

Question

So, as a task for C, I need to create a card game. Naturally, shuffling be an important part of the code.

I designed the deck to hold cards 52 cards (no jokers), which were identified as integers:

Hundreds would represent the suit, while the tens and ones would represent the face.

I started out by plugging in these numbers into the deck in order first, then shuffled it with a code that basically takes the number from two random indexes in the array and swaps them. This swapping loops for a million times.

However, for some odd reason, after shuffling, the number 0 (Ace of Spades) would always appear twice after shuffling. I wrote a debugging code that would alert when two elements are identical in the array, and it is always 0.

I look through my code over and over, and I can't seem to find the reason why. Is there a characteristic of C that I'm not noticing?

Code:

/* Suit and Face legend:
 Suits
  000 - Spade
  100 - Clover
  200 - Diamond 
  300 - Heart
 Faces
   0 - Ace
   1 - 2
   2 - 3
   3 - 4
   4 - 5
   5 - 6
   6 - 7
   7 - 8
   8 - 9
   9 - 10
   10 - Jack
   11 - Queen
   12 - King
*/

#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <stdlib.h>
#include <time.h>

#define SUITS 4
#define FACES 13
#define CARDS 52
#define MONEY 500

void debugPrintDeck();

static int deck[CARDS];//deck used in game

int main(){

    //Variables
    int cnt = -1; //Keeps track of how many cards there are in the deck, as well as the nth card on top. -1 if there's no card in the deck. 0 indexing.

   srand(time(0));

    puts("Stacking deck in order...");

    //PLACING CARDS IN ORDER IN DECK (First Step)
    for(int crd = -1; crd < 312;){//Starting from the first Spade (000) to Heart (300)
        crd++; //Starts with Ace.
        cnt++; //indicating a card has been added to the deck.
        deck[cnt] = crd;
        if(crd == 12 || crd == 112 || crd == 212 || crd == 312) crd += 87;
    }

    debugPrintDeck();

    puts("\nShuffling in progress...");

    //SHUFFLING CODE (Second Step)
    //Includes code that will print the values that switch.
    //Also include code that will terminate the program when it detects identical numbers in different indexes.
    for (int shfl = 1; shfl < 1000000; shfl++){
        int rng1 = -1; //initialize to a value not in the deck.
        int rng2 = -1;
        int temp1 = -1;
        int temp2 = -1;
        do{
            rng1 =  rand() % 53;
            rng2 =  rand() % 53;
        } while (rng1 == rng2); //ensures the values won't randomize into the same position.
        temp1 = deck[rng1];
        temp2 = deck[rng2];
        printf("\ntemp1 at deck[%d]= %d",rng1, temp1); //debug
        printf(" temp2 at deck[%d]=%d",rng2, temp2); //debug
        deck[rng2] = temp1;
        deck[rng1] = temp2;
        if (deck[rng2] == deck[rng1]) { //debug
          printf("\nALERT ALERT ALERT: rng1 #%d is %003d, rng2 #%d is %003d", rng1, deck[rng1], rng2, deck[rng2]);
          exit(0);
          }
    }

    debugPrintDeck();

}

void debugPrintDeck(){
    puts("\nThe following is the full stack of cards from end to end.");
    for (int card = 0; card < 52; card++){
        printf("\ncard #%d = %003d", card, deck[card]);
    }
}

Note: If you want the program to complete the shuffling and terminate properly, just remove line 82.