To reproduce:
- Add RadGridView to a blank project and bind it to a blank binding source.
- Add GridViewMultiComboBoxColumn to the grid and bind it to another binding source.
- In the CellEditorInitialized set the autocomplete mode to Suggest.
- When you start the application you will notice that the first items is selected but not displayed and to display it you should select other value first and you will be able to select the first one.

Workaround:
Set the selected item of the editor to null in the CellEditorInitialized event.