The Grid will throw a JavaScript error if the user wants to group and drops a column header near the edges of the grouping header or between existing group chips.

This is a regression in version 6.0.0.

REPL test page: https://blazorrepl.telerik.com/wouBdbvw36O4UaAR14

A possible workaround is to remove the empty space, which triggers the error, so that users cannot drop on it:

CSS

    .k-grid .k-grouping-header {
        padding: 0;
        border-bottom-width: 0;
        gap: 0;
    }

        .k-grid .k-grouping-header::before {
            margin: 0;
        }

    .k-grid .k-grouping-header .k-grouping-drop-container {
        margin: 0;
    }