To reproduce: use the attached sample project. Follow the steps illustrated on the attached gif file.

Workaround: keep the vertical scrollbar value and maximum before modifying the child rows and restore them afterwards:

private void gridViewParameter_CellValueChanged(object sender, GridViewCellEventArgs e)
{
   if (e.Column.Name == "Select")
    {
        this.gridViewParameter.CellValueChanged -= gridViewParameter_CellValueChanged;

        GridViewRowInfo selectedRowinfo = e.Row;                  
        if (selectedRowinfo.HasChildRows())
        {
            int scrollValue = this.gridViewParameter.TableElement.VScrollBar.Value;
            int scrollMax = this.gridViewParameter.TableElement.VScrollBar.Maximum;
          
            this._UpdateUiState(selectedRowinfo.ChildRows, Convert.ToBoolean(selectedRowinfo.Cells["Select"].Value));
            
            this.gridViewParameter.TableElement.VScrollBar.Maximum = scrollMax;
            this.gridViewParameter.TableElement.VScrollBar.Value = scrollValue;
        }
        this.gridViewParameter.CellValueChanged += gridViewParameter_CellValueChanged;
    }
}

NOTE: after applying the workaround, there is annoying flickering illustrated on the Flickering.gif file which should be handled if possible.