https://stackblitz.com/edit/angular-obj4gecf

If you click the first 2 cells in column "UnitPrice", the first one reports column 2 (which is correct), the second reports column 1.

I suspect rowSpan causes this, rows without rowSpan seem to work.

When filter popup is opened, it need to be closed by click outside of it

However, popup is closed only after second click outside.

After popup was opened and closed for the first time - next times everything works correctly, so it can be reproduced only after refreshing the page with this component

It can be reproduced in example in your documentation: https://www.telerik.com/kendo-angular-ui/components/grid/filtering/filter-menu/#toc-custom-filters/