Make Ai pick edges first, but miniMax doesn't pick optimal next move

[aquaductape]

Usually the Ai moves on corners or center on it's first move. I wanted the make the ai move to the edges instead on the first turn, so I hard coded the ai to move on a particular edge, but for some reason this causes next move of the ai to be suboptimal.

//global variable
let onlyFirstMove = true
...
if (OPPONENT == "computer") {
    // get id of space using minimax algorithm
    let id = minimax(gameData, player.computer).id;
    if (onlyFirstMove) {
    id = 3;
    onlyFirstMove = false;
    }

    // store the player's move to gameData
    gameData[id] = player.computer;
...

turn 2: Ai player is hard coded to move on a2
   a     b     c
      |     |     
1  -  |  x  |  -  
 _____|_____|_____
      |     |     
2  o  |  -  |  -  
 _____|_____|_____
      |     |     
3  -  |  -  |  -  
      |     |    

turn 3: Human player picks b2

   a     b     c
      |     |     
1  -  |  x  |  -  
 _____|_____|_____
      |     |     
2  o  |  x  |  -  
 _____|_____|_____
      |     |     
3  -  |  -  |  -  
      |     |     

turn 4: Ai player picks a1, when it should have picked b3

   a     b     c
      |     |     
1  o  |  x  |  -  
 _____|_____|_____
      |     |     
2  o  |  x  |  -  
 _____|_____|_____
      |     |     
3  -  |  -  |  -  
      |     |