To reproduce:

DataTable dt = new DataTable();

public Form1()
{
    InitializeComponent();
    
    dt.Columns.Add("Id");
    dt.Columns.Add("Name");
    dt.Columns.Add("Type");
    for (int i = 0; i < 30; i++)
    {
        dt.Rows.Add(i, "Item" + i, "Type" + i % 2);
    }

    this.radGridView1.DataSource = dt;
    this.radGridView1.AutoExpandGroups = true;
    GroupDescriptor descriptor = new GroupDescriptor();
    descriptor.GroupNames.Add("Type", ListSortDirection.Ascending);
    this.radGridView1.GroupDescriptors.Add(descriptor);
}

private void button1_Click(object sender, EventArgs e)
{
    dt.Rows.Add(30, "Item30", "Type3");
}

Workaround: set the AutoExpandGroups property to false and manually expand the groups when a new row is added.