I am unable to have the onItemClick event fire when selecting an item from the DropDownButton.
In my app the onItemClick seems to only fire if I double click on the item super fast. The item is contained within a bootstrap modal.
Your own demo appears to exhibit this same behavior as the Event Log never shows "item click" (https://www.telerik.com/kendo-react-ui/components/buttons/dropdownbutton/events/).