This bug still persists in the ActiveX OCX 15.3.1. When scrolling the combobox with the mouse in Markup mode, then there is some additional "backwards" scrolling going on. Dragging the scrollbar slider doesn't exhibit this behavior.

Please fix this annoying scroll behavior.

Here is some VB6 code to produce such a combobox, that shows the above problem:

Private Sub CreateCombo()
    Dim s As String
    Dim k As Long
    Dim m As String

    With cb
      .Clear
      .EnableMarkup = True
      .DropDownWidth = cb.Width
    End With

    For k = 1 To 100
      cb.AddItem Format(k, "000") & " - This is item " & k
      cb.ItemData(cb.NewIndex) = k

      m = "<Grid>" & _
      " <Grid.ColumnDefinitions>" & _
      " <ColumnDefinition Width='35'/>" & _
      " <ColumnDefinition />" & _
      " </Grid.ColumnDefinitions>" & _
      " <Grid.RowDefinitions>" & _
      " <RowDefinition/>" & _
      " </Grid.RowDefinitions>" & _
      " <TextBlock TextAlignment='Left' FontFamily='Tahoma' FontSize='10' FontWeight='Bold'>" &       Format(k, "000") & "</TextBlock>" & _
      " <TextBlock TextAlignment='Left' FontFamily='Tahoma' FontSize='10' Grid.Column='1'>" & "This is item " & k & "</TextBlock>" & _
      "</Grid>"

      cb.MarkupList(cb.NewIndex) = m
    Next
End Sub