csharp DataGridView - DataTable.GetChanges returns null.

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C#

SQL-Server

DataGridView

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DataTable.GetChanges returns null sometimes even though changes have been made.

1.Edit a cell in first row (C,1), change is applied and saves successfully to DB. Cursor moves to cell (C,2) on return.
This is more odd than I thought as DataTable changeTable = DataTableTopLevel.GetChanges(); returns null, but it still saves
2.Edit a cell in second row (C,2), value changes back on return key. Also cursor does not move to (C,3) BUT moves to (A,3).
DataTable changeTable = DataTableTopLevel.GetChanges(); returns non null, but is not saved.
3.Edit a cell in third row (C,3), change is applied and saves successfully to DB. Cursor moves to cell (C,4) on return.

public partial class MeServerMainForm : Form
 {

     string connServer;
     string qryServerTopLevel;
     string qryServerBottomLevel;
     SqlDataAdapter SqlAdapterTopLevel;
     SqlDataAdapter SqlAdapterBottomLevel;
     SqlCommandBuilder SqlCommandBuilderTopLevel;
     SqlCommandBuilder SqlCommandBuilderBottomLevel;
     DataTable DataTableTopLevel;
     DataTable DataTableBottomLevel;
     BindingSource BindingSourceTopLevel;
     BindingSource BindingSourceBottomLevel;

     bool TopLevelCellValueChanged;

     public MeServerMainForm()
     {
         InitializeComponent();
         InitData();
         TopLevelCellValueChanged = false;
     }

     public void InitData()
     {
         //create the connection string
         connServer = "Data Source=192.168.0.11;Initial Catalog=Phil;User Id=Philip;Password=Philip;";

         // TOP LEVEL
         //create the database query
         qryServerTopLevel = @"SELECT
                                             MeID
                                             ,MeTypeID
                                             ,MeTitle
                                             ,CreatedDateTime
                                             ,ReadOnly
                                             ,ParentMeID
                                             ,Question
                                             ,Answer
                                             ,MeScore
                                             ,MeLastTestDate
                                         FROM MyMees
                                         WHERE ParentMeID = 0 ";

         //create an OleDbDataAdapter to execute the query
         SqlAdapterTopLevel = new SqlDataAdapter(qryServerTopLevel, connServer);
         //create a command builder
         SqlCommandBuilderTopLevel = new SqlCommandBuilder(SqlAdapterTopLevel);
         //create a DataTable to hold the query results
         DataTableTopLevel = new DataTable();
         //fill the DataTable
         SqlAdapterTopLevel.Fill(DataTableTopLevel);
         //BindingSource to sync DataTable and DataGridView
         BindingSourceTopLevel = new BindingSource();
         //set the BindingSource DataSource
         BindingSourceTopLevel.DataSource = DataTableTopLevel;
         //set the DataGridView DataSource
         DataGridViewTopLevel.DataSource = BindingSourceTopLevel;

         // Bottom LEVEL
         //create the database query
         qryServerBottomLevel = @"SELECT
                                             MeID
                                             ,MeTypeID
                                             ,MeTitle
                                             ,CreatedDateTime
                                             ,ReadOnly
                                             ,ParentMeID
                                             ,Question
                                             ,Answer
                                             ,MeScore
                                             ,MeLastTestDate
                                         FROM MyMees
                                         WHERE ParentMeID = 2 ";

         //create an OleDbDataAdapter to execute the query
         SqlAdapterBottomLevel = new SqlDataAdapter(qryServerBottomLevel, connServer);
         //create a command builder
         SqlCommandBuilderBottomLevel = new SqlCommandBuilder(SqlAdapterBottomLevel);
         //create a DataTable to hold the query results
         DataTableBottomLevel = new DataTable();
         //fill the DataTable
         SqlAdapterBottomLevel.Fill(DataTableBottomLevel);
         //BindingSource to sync DataTable and DataGridView
         BindingSourceBottomLevel = new BindingSource();
         //set the BindingSource DataSource
         BindingSourceBottomLevel.DataSource = DataTableBottomLevel;
         //set the DataGridView DataSource
         DataGridViewBottomLevel.DataSource = BindingSourceBottomLevel;

         DataTableTopLevel.AcceptChanges();
     }

     private void loadMeTreeToolStripMenuItem_Click(object sender, EventArgs e)
     {

     }

     private void DataGridViewTopLevel_RowLeave(object sender, DataGridViewCellEventArgs e)
     {

         DataTable changeTable = DataTableTopLevel.GetChanges();
         if (changeTable != null)
         {
             SqlAdapterTopLevel.Update(DataTableTopLevel);
             DataTableTopLevel.AcceptChanges();
             DataTableTopLevel.Clear();
             SqlAdapterTopLevel.Fill(DataTableTopLevel);
             TopLevelCellValueChanged = false;

         }




     }

Any ideas?
Thanks
Phil