possible bug--please help!!!

[day]

Hello!  I have never submitted a bug before so please let me know if  
you need more details from me.

Background: I am calling gawk from a script (#!/bin/gawk).  My input  
file, as viewed from VIM, is 439 lines long.  On each line are  
uppercase letters with no spaces.
Example Input: ABCERFDHDSAEGJKL

My desired output is a newly created line that is alphabetized and unique.
Example Output: ABCDEFGHJKLRS

In order to do this, I read input into an array, like this.

gawk 'BEGIN {FS = "" ; RS = "\n"};
{
    for(x=1;x<=NF;x++)
    {
        array[x]=$x
    };
    asort(array);
    for(y=1;y<=NF;y++)
    {
        printf"%c",array[y]
    };
    printf"\n"
}

For the most part, this works, except for the first time there is some  
sort of repetition.  Occasionally, my output becomes ABCDEFGHJKLRP.   
The last letter is swapped!  This renders my awk program completely  
useless.  Is this a bug or am I screwing something up here?

Thank you so much for your time!

Best,

Natt