LUCKPAL: Getting wrong answer

I have tried so many examples seems right. Can’t figure out why i am getting a WA. Basically my approach is to have a sliding window of size 5. I just iterate through the word and check these condition:

  1. if current index within the sliding window:
    -make ‘lucky’ starting that window and also make ‘ykcul’ in the corresponding place in string
    - also track the changes count
  2. else // non lucky region :
    -see if the character at this index and (strlen - index) match
    -if(no match) increase count of changes and make substitution of either char at index to (strlen - index) or vice versa depending upon which is greater

simple condition to return “unlucky” is to see if the size of the string is less than 9