My custom sorting function doesnot work

[Estasie]

Hi, I'm using table with custom sorting, passing the parameter

                legendComparator: (rowA, rowB, columnId) => {
                    if (
                        rowA.original.type === 'Total' ||
                        rowB.original.type === 'Total' ||
                        rowA.original.type === 'GroupHeader' ||
                        rowB.original.type === 'GroupHeader'
                    ) {
                        return 0;
                    }

                    return legendRowsComparator(rowA.original, rowB.original, columnId as any);
                },
            },

And using this sort at my columns:

export const ALIAS_COLUMN: ColumnDef<LegendRow> = {
   accessorKey: 'alias',
   header: 'Alias',
   enableSorting: true,
   size: 1000,
   maxSize: 1000,
   sortingFn: 'legendComparator', // usage
   cell: ({row}) => (isLegendDataRow(row.original) ? <RowCell row={row.original} /> : null),
};

Unfortunately, data at the table doesnot sort properly - Total/GroupHeader types of rows are still participant at sorting (they should not, and must be at their places). But my data, that I pass to the table is sorting correctly (i handle it via redux). What am I doing wrong...?
Please, help me, I almost gave up

also - my comporator function

export const legendRowsComparator = (rowA: LegendRow, rowB: LegendRow, column: keyof LegendDataRow): number => {
   if (!isLegendDataRow(rowA) || !isLegendDataRow(rowB)) { // here i check if there is a type field inside the row
       return 0;
   }
   if (rowA.yAxis !== rowB.yAxis) {
       return 0;
   }

   const labelName = column.startsWith(`${PREFIX}.`)
       ? column.slice(PREFIX.length + 1)
       : '';
   const leftItem = labelName ? rowA.labels?.[labelName] : rowA[column];
   const rightItem = labelName ? rowB.labels?.[labelName] : rowB[column];

   // when row.count is 0, the line is empty, and all the statistics make
   // no sense to be displayed
   if ((rowA.count === 0 || rowB.count === 0) && (SPECIAL_COLUMNS as readonly string[]).includes(column)) {
       return rowA.count === 0 ? 1 : -1;
   }

   if (leftItem !== undefined && rightItem !== undefined) {
       return leftItem > rightItem ? -1 : 1;
   } else if (leftItem === undefined && rightItem !== undefined) {
       return 1;
   } else if (leftItem !== undefined && rightItem === undefined) {
       return -1;
   }
   return 0;
};

[Estasie]

It looks I have found the solution. I did set sortUndefined: false for my columns. So if u have service columns it might be useful!!!!