C# datagridview saving blank records

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C#

DataGridView

I am developing a C# WinForms Solution in VS 2015 Professional. In on my my forms, I have a DataGridView that is not correctly saving the rows. After I enter data and save, it saves blank cells. This started happening after I implemented the code below. I appreciate your time and help. Thank you!

What I have tried:

private void Alunos_Load(object sender, EventArgs e)

       {
           this.tbl_cursosTableAdapter.Fill(this.bremingtonDataSet.tbl_cursos);
           this.tbl_modulosTableAdapter.Fill(this.bremingtonDataSet.tbl_modulos);
           this.tbl_turmasTableAdapter.Fill(this.bremingtonDataSet.tbl_turmas);
           this.tbl_alunosTableAdapter.Fill(this.bremingtonDataSet.tbl_alunos);
           this.tbl_alunos_subTableAdapter.Fill(this.bremingtonDataSet.tbl_alunos_sub);

           DataView dv = new DataView(bremingtonDataSet.Tables["tbl_modulos"]);
           filteredModulosBS.DataSource = dv;
      }

       private void tbl_alunos_subDataGridView_CellBeginEdit(object sender, DataGridViewCellCancelEventArgs e)
       {
           if (e.ColumnIndex == comboBoxModulo.Index)
           {
               DataGridViewComboBoxCell dgcb = (DataGridViewComboBoxCell)tbl_alunos_subDataGridView[e.ColumnIndex, e.RowIndex];
               dgcb.DataSource = filteredModulosBS;
               this.filteredModulosBS.Filter = "CodCurso=" + this.tbl_alunos_subDataGridView[e.ColumnIndex - 1, e.RowIndex].Value.ToString();
           }
       }

   private void tbl_alunos_subDataGridView_CellEndEdit(object sender, DataGridViewCellEventArgs e)
   {
       if (e.ColumnIndex == this.comboBoxModulo.Index)
       {
           DataGridViewComboBoxCell dgcb = (DataGridViewComboBoxCell)tbl_alunos_subDataGridView[e.ColumnIndex, e.RowIndex];
           dgcb.DataSource = tblmodulosBindingSource;
           this.filteredModulosBS.RemoveFilter();
       }
   }