When the user is using the MultiColumnComboBox, if they open the combo box, then use the arrow keys to highlight a row in the grid, but then change their mind and hit escape to close the dropdown, then want to move to the next field so they hit tab, it then selects the last record that was highlighted in the grid. This seems like a bug to me. The docs for this control say "Escape: Pressing Escape will close the DropDown and the matched item would not be selected."
If the user can't tab out of the field without selecting a record, how can they leave the field without selecting a record with just the keyboard?
I was able to duplicate this functionality in the demo app. See zipped GIF in the attachments.