DataGridViewComboBoxColumn using different datasource - Combobox loose value when loose focus

I have a DataGridView with a ComboBox Column, binded to a bindingsource. The combobox are filled each with different list of Item. I'm having now an issue, since the value I select in the combo get lost as soon as i change the grid row. If i select again the row, the value is displayed back.

Each combo in the grid is populated using different list of items. I found that the issue is related to the fact that the value i select does not exist in the other combobox.

Any help will be very very appreciated, since i am not able to find a solution. Following you ca find a simple example to reproduce my issue:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        List<TestDataSource> ds = new List<TestDataSource>();

            TestDataSource i = new TestDataSource();
            i.Text = "Text1";

            IDValore iv = new IDValore();
            iv.id = "id1";
            iv.val = "val1";

            IDValore iv2 = new IDValore();
            iv2.id = "id2";
            iv2.val = "val2";

            i.ValueList.Add(iv);
            i.ValueList.Add(iv2);


            TestDataSource i2 = new TestDataSource();
            i2.Text = "Text2";

            IDValore iv3 = new IDValore();
            iv3.id = "id1";
            iv3.val = "val1";

            IDValore iv4 = new IDValore();
            iv4.id = "id4";
            iv4.val = "val4";

            i2.ValueList.Add(iv3);
            i2.ValueList.Add(iv4);

            ds.Add(i);
            ds.Add(i2);

            testDataSourceBindingSource.DataSource = ds;
    }



    private void dataGridView1_DataError(object sender, DataGridViewDataErrorEventArgs e)
    {

    }

}

public class TestDataSource
{
    public String Text { get; set; }

    public List<IDValore> ValueList { get; set; }

    public TestDataSource()
    {
        Text = String.Empty;
        ValueList = new List<IDValore>();
    }
}

public class IDValore
{
    public String id { get; set; }
    public String val { get; set; }
}

#region Windows Form Designer generated code

    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
        this.components = new System.ComponentModel.Container();
        this.valoriBindingSource = new System.Windows.Forms.BindingSource(this.components);
        this.dataGridView1 = new System.Windows.Forms.DataGridView();
        this.testDataSourceBindingSource = new System.Windows.Forms.BindingSource(this.components);
        this.textDataGridViewTextBoxColumn = new System.Windows.Forms.DataGridViewTextBoxColumn();
        this.ComboColumn = new System.Windows.Forms.DataGridViewComboBoxColumn();
        ((System.ComponentModel.ISupportInitialize)(this.valoriBindingSource)).BeginInit();
        ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).BeginInit();
        ((System.ComponentModel.ISupportInitialize)(this.testDataSourceBindingSource)).BeginInit();
        this.SuspendLayout();
        // 
        // valoriBindingSource
        // 
        this.valoriBindingSource.DataMember = "ValueList";
        this.valoriBindingSource.DataSource = this.testDataSourceBindingSource;
        // 
        // dataGridView1
        // 
        this.dataGridView1.AllowUserToAddRows = false;
        this.dataGridView1.AllowUserToDeleteRows = false;
        this.dataGridView1.AutoGenerateColumns = false;
        this.dataGridView1.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
        this.dataGridView1.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] {
        this.textDataGridViewTextBoxColumn,
        this.ComboColumn});
        this.dataGridView1.DataSource = this.testDataSourceBindingSource;
        this.dataGridView1.EditMode = System.Windows.Forms.DataGridViewEditMode.EditOnEnter;
        this.dataGridView1.Location = new System.Drawing.Point(12, 26);
        this.dataGridView1.Name = "dataGridView1";
        this.dataGridView1.SelectionMode = System.Windows.Forms.DataGridViewSelectionMode.FullRowSelect;
        this.dataGridView1.Size = new System.Drawing.Size(345, 143);
        this.dataGridView1.TabIndex = 0;
        this.dataGridView1.DataError += new System.Windows.Forms.DataGridViewDataErrorEventHandler(this.dataGridView1_DataError);
        // 
        // testDataSourceBindingSource
        // 
        this.testDataSourceBindingSource.DataSource = typeof(UnitTest.TestDataSource);
        // 
        // textDataGridViewTextBoxColumn
        // 
        this.textDataGridViewTextBoxColumn.DataPropertyName = "Text";
        this.textDataGridViewTextBoxColumn.HeaderText = "Text";
        this.textDataGridViewTextBoxColumn.Name = "textDataGridViewTextBoxColumn";
        this.textDataGridViewTextBoxColumn.ReadOnly = true;
        this.textDataGridViewTextBoxColumn.Width = 150;
        // 
        // ComboColumn
        // 
        this.ComboColumn.DataSource = this.valoriBindingSource;
        this.ComboColumn.DisplayMember = "val";
        this.ComboColumn.HeaderText = "ComboColumn";
        this.ComboColumn.Name = "ComboColumn";
        this.ComboColumn.ValueMember = "id";
        this.ComboColumn.Width = 150;
        // 
        // Form1
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(1026, 573);
        this.Controls.Add(this.dataGridView1);
        this.Name = "Form1";
        this.Text = "Form1";
        this.Load += new System.EventHandler(this.Form1_Load);
        ((System.ComponentModel.ISupportInitialize)(this.valoriBindingSource)).EndInit();
        ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).EndInit();
        ((System.ComponentModel.ISupportInitialize)(this.testDataSourceBindingSource)).EndInit();
        this.ResumeLayout(false);

    }

    #endregion

    private System.Windows.Forms.BindingSource valoriBindingSource;
    private System.Windows.Forms.BindingSource testDataSourceBindingSource;
    private System.Windows.Forms.DataGridView dataGridView1;
    private System.Windows.Forms.DataGridViewTextBoxColumn textDataGridViewTextBoxColumn;
    private System.Windows.Forms.DataGridViewComboBoxColumn ComboColumn;