To reproduce:
- Add some columns to the grid, make sure that most of the columns are not visible (the user must scroll to view them).
- Drag and drop the second column at the last position in the grid.
- The result can be seen on the attached image. 

Workaround:

Private Sub Columns_CollectionChanged(ByVal sender As Object, ByVal e As Telerik.WinControls.Data.NotifyCollectionChangedEventArgs)
      Me.RadGridView1.TableElement.ViewElement.UpdateRowsWhenColumnsChanged()
End Sub