Unity enumがちゃんと動いていない？

私は今、ステージセレクトのプログラムを組んでおります。
ソースを転記しておきます。
/*==============================================
//      列挙型  
==============================================*/
public enum STAGESELECT_MODE{
    STAGE, SHOP, MODE, DIFFICULTY,
}
public enum STAGE{
    STAGE1, STAGE2, STAGE3,MAX_STAGE
}
public enum DIFFICULTY{
    EASY,NORMAL,HARD
}
public STAGESELECT_MODE stageselect_Mode = STAGESELECT_MODE.STAGE;
public STAGE stage_No = STAGE.STAGE1;
public DIFFICULTY difficulty_No = DIFFICULTY.EASY;

/// <summary>
    /// ステージセレクトの主な動き
    /// </summary>
    public void StageSelect_Main()
    {
        switch(stageselect_Mode)
        {
            case STAGESELECT_MODE.STAGE:
                StageSelect_Stage();
                break;

            case STAGESELECT_MODE.DIFFICULTY:

                break;
        }
    }

    /// <summary>
    /// ステージセレクトのステージ・おみせ・モード画面の選択
    /// </summary>
    public void StageSelect_Stage()
    {
        if (Input.GetKeyDown(KeyCode.UpArrow))
        {
            if (stageselect_Mode == STAGESELECT_MODE.SHOP)
            {
                stageselect_Mode = STAGESELECT_MODE.STAGE;
                stage_No = STAGE.STAGE1;
                cursor.MoveCursol(cursor_pos_x[0], cursor_pos_y[0]);
            }
            else if (stageselect_Mode == STAGESELECT_MODE.MODE)
            {
                stageselect_Mode = STAGESELECT_MODE.STAGE;
                stage_No = STAGE.STAGE3;
                cursor.MoveCursol(cursor_pos_x[2], cursor_pos_y[2]);
            }
        }
        if (Input.GetKeyDown(KeyCode.DownArrow))
        {
            if (stageselect_Mode == STAGESELECT_MODE.STAGE)
            {
                if (stage_No == STAGE.STAGE1 || stage_No == STAGE.STAGE2)
                {
                    stageselect_Mode = STAGESELECT_MODE.SHOP;
                    cursor.MoveCursol(cursor_pos_x[3], cursor_pos_y[3]);
                }
                else if (stage_No == STAGE.STAGE3)
                {
                    stageselect_Mode = STAGESELECT_MODE.MODE;
                    cursor.MoveCursol(cursor_pos_x[4], cursor_pos_y[4]);
                }
            }
        }

        if (Input.GetKeyDown(KeyCode.LeftArrow))
        {
            if (stageselect_Mode == STAGESELECT_MODE.STAGE)
            {
                if (stage_No == STAGE.STAGE2)
                {
                    stage_No = STAGE.STAGE1;
                    cursor.MoveCursol(cursor_pos_x[0], cursor_pos_y[0]);
                }
                else if (stage_No == STAGE.STAGE3)
                {
                    stage_No = STAGE.STAGE2;
                    cursor.MoveCursol(cursor_pos_x[1], cursor_pos_y[1]);
                }
            }
            else if(stageselect_Mode == STAGESELECT_MODE.MODE)
            {
                stageselect_Mode = STAGESELECT_MODE.SHOP;
                cursor.MoveCursol(cursor_pos_x[3], cursor_pos_y[3]);
            }

        }
        if (Input.GetKeyDown(KeyCode.RightArrow))
        {
            if (stageselect_Mode == STAGESELECT_MODE.STAGE)
            {
                if (stage_No == STAGE.STAGE1)
                {
                    stage_No = STAGE.STAGE2;
                    cursor.MoveCursol(cursor_pos_x[1], cursor_pos_y[1]);
                }
                else if (stage_No == STAGE.STAGE2)
                {
                    stage_No = STAGE.STAGE3;
                    cursor.MoveCursol(cursor_pos_x[2], cursor_pos_y[2]);
                }
            }
            else if (stageselect_Mode == STAGESELECT_MODE.SHOP)
            {
                stageselect_Mode = STAGESELECT_MODE.MODE;
                cursor.MoveCursol(cursor_pos_x[4], cursor_pos_y[4]);
            }
        }
        //決定キーで難易度選択へ
        if (Input.GetKeyDown(KeyCode.Keypad5) || Input.GetKeyDown(KeyCode.Alpha5))
        {
            stageselect_Mode = STAGESELECT_MODE.DIFFICULTY;
        }
    }
cursor.MoveCursolはカーソルを指定した場所に動かすプログラム。
今回のとは関係はないとみられるので割愛。
このプログラムですと、stageselect_ModeがSTAGESELECT_MODE.STAGEの場合は作動するのですが、stageselect_Modeがstageselect_Mode = STAGESELECT_MODE.MODEやstageselect_Mode == STAGESELECT_MODE.SHOPになると入力しているのにも関わらず、ちゃんと作動しないのです。

このような原因はどのようなことが考えられますか？教えて頂けないでしょうか？
詳しい解説並びにソースを書いていただくと幸いです。