Consider the game of Tic-Tac-Toe below. Most human players would, in this position, play in cell (1, 2) to block X from getting three-in-a-row there. Suppose you gave this position to a Minimax solver, and Minimax suggested that you play in cell (0, 0) instead.
Even though it might seem like your Minimax implementation is buggy, it might not be! Why might Minimax suggest a move other than (1, 2) in this position?