I had to save the board state for each move made when Minimax was called and analyze them individually. This allowed me to track the moves and notice that the board state was not being updated correctly. I’ve now resolved the issue. The problem was related to how I was passing my board state (piecesPos). I was retrieving and passing the wrong board state, which caused Minimax to make incorrect or suboptimal moves. Thank you all for your contributions; it is greatly appreciated.

Renaming to piecesPosCopy and using piecesPos

This was getting the actual board state to use when min max is called.

int minMax(List<String> piecesPosCopy, int depth, bool isMaximizing, int alpha, int beta) {
    // Base case: if depth is 0 or the game is over, return the evaluation
    if (depth == 0 || isGameOver(piecesPos)) {
      return evaluateBoard(piecesPos);
    }

    if (isMaximizing) {
      int maxEval = -9999; // Initialize to a very low value
      for (int i = 0; i < piecesPos.length; i++) {
        if (piecesPos[i][0] == "B" || piecesPos[i][0] == "O") {
          List<int> possibleMoves = getPossibleMoves(piecesPos, i);
          for (int move in possibleMoves) {
            // Save the current state
            List<String> saveState = List.from(piecesPos);

            // Make the move
            performMultitakeAnim = false;
            makeMove(piecesPos, i, move);

            // Recursive call
            int eval = minMax(piecesPos, depth - 1, false, alpha, beta);

            // Restore the state
            piecesPos = List.from(saveState);

            // Update maxEval
            maxEval = max(maxEval, eval);
            alpha = max(alpha, eval);

            // Alpha-Beta Pruning
            if (beta <= alpha) {
              break;
            }
          }
        }
      }
      return maxEval;
    } else {
      int minEval = 9999; // Initialize to a very high value
      for (int i = 0; i < piecesPos.length; i++) {
        if (piecesPos[i][0] == "W" || piecesPos[i][0] == "Q") {
          List<int> possibleMoves = getPossibleMoves(piecesPos, i);
          for (int move in possibleMoves) {
            // Save the current state
            List<String> saveState = List.from(piecesPos);

            // Make the move
            performMultitakeAnim = false;
            makeMove(piecesPos, i, move);

            // Recursive call
            int eval = minMax(piecesPos, depth - 1, true, alpha, beta);

            // Restore the state
            piecesPos = List.from(saveState);

            // Update minEval
            minEval = min(minEval, eval);
            beta = min(beta, eval);

            // Alpha-Beta Pruning
            if (beta <= alpha) {
              break;
            }
          }
        }
      }
      return minEval;
    }
  }