C# Random Number Gen stops after 12 button clicks

Working on homework assignment and random number generator stops populating TestBox after 12 button clicks?? This happens every single time I run it and I have no idea why. Also if anything looks sloppy please say so.

public partial class GuessANumber : Form
{
    int[] array = new int[100];
    public GuessANumber()
    {
        InitializeComponent();
        array = RandomArray();
        this.Gen_Rand.Click += new EventHandler(this.Gen_Rand_Click);
    }

    public int[] RandomArray()
    {            
        Random rand = new Random();
        for (int i = 0; i < array.Length; i++)
        {
            array[i] = rand.Next(1, 100);
        }
        return array;
    }

    private void Form1_Load(object sender, EventArgs e)
    {}

    private void Gen_Rand_Click(object sender, EventArgs e)
    {
        array = RandomArray();
        for (int i = 0; i < array.Length; i++)
        {
            TestBox.AppendText(" " + Convert.ToString(array[i]));
        }
    }
}