datagridview comboboxcolumn dropdown not work properly

hi dear

I have a problem in my program, and that is that in the datagridview combobox column, in the on EditingControlShowing event, I cast to datagridviewcomboboxedintgcontrol and set DroppedDown=true, but this combobox does not always open and always has the value of the dropdown and items, but sometimes it does not drop down, even when I call it.

Private Async Sub vsfGoodList_EditingControlShowing(sender As Object, e As DataGridViewEditingControlShowingEventArgs) Handles vsfGoodList.EditingControlShowing
Application.Update(Me, Async Sub()
If e.Control IsNot Nothing Then
If TypeOf e.Control Is Wisej.Web.DataGridViewComboBoxEditingControl Then
Dim comboCell As ComboBox = DirectCast(e.Control, ComboBox)
If comboCell IsNot Nothing Then
comboCell.AutoCompleteMode = Wisej.Web.AutoCompleteMode.Filter
comboCell.DroppedDown = True
End If

‘ comboCell.Focus()
End If
End If
End Sub)
End Sub

if async or sync sometimes  not work but items exists

Best regards