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Minimax/MinMax Algorithm not working correctly

Hey everyone, I realize this is probably above Treehouse's paygrade, but I'll ask anyways:

As a practice project I made a Tic-Tac-Toe game on JSFiddle and I progressed into adding an unbeatable AI. For the most part it works, but there are some combinations (e.g. setting X into fields 5, 9, 3 or into fields 3, 7, 9) that lead to the computer not calculating the optimal move properly.

The project on JSFiddle: https://jsfiddle.net/jd8x0vjz/

I think the function starting at line 63 (the one that evaluates the effectiveness of a move) is causing problems:

function evaluateMove(move, player, depth) {
var gameStatus = evaluateGameStatus(move); //get status of current board
if (gameStatus < 2 && player)
    return -1; //if human won, return -1
if (gameStatus < 2 && !player)
    return 1; //if human lost, return 1

var returnValue = 0 //value to be returned later

for (var z = 0; z < 3; z++) { //loop for row
    for (var s = 0; s < 3; s++) { //loop for column
        if (move[z][s]) //if current slot has an x or o,
            continue; //skip it     
        var nextMove = cloneGameStatus(move); //create temporary array with base of current grid
        nextMove[z][s] = !player ? "x" : "o"; //assign first free field  the appropriate symbol
        var value = evaluateMove(nextMove, !player, depth+1);   //recursion but with switched player, to add the correct icon afterwards
        if ((value > returnValue) && player)
            returnValue = value;            
        if ((value < returnValue) && !player)
            returnValue = value;                
return returnValue; //return value of current simulation

However, I don't know why some combinations cause the computer to miscalculate. Any help would be greatly appreciated!!