As per the heading, all the demos on the KendoReact MultiColumnComboBox have a lot of hardcoded data which results in a scrollbar being rendered in the popup. If you only have a few items, then no scrollbar is rendered and the column headers are misaligned with the data rows:
https://stackblitz.com/edit/react-gwftb5?file=app%2Fmain.tsx
Kind regards,
David