Treegrid Sorting Working differently for str and int

Treegrid Sorting Working differently for str and int. For numbers it sorts only within the grouping and with strings it is re sorting the groups.

I want the main groups to stay in one spot. I tried changing smart rendering, changing stable sorting, and doing
grid.attachEvent(
‘onAfterSorting’,
function(index, type, direction) {
grid.sortTreeRows(0, ‘str’, ‘desc’);
}
);

Please open ticket at support.dhtmlx.com/ and provide us complete demo where we can reproduce this issue.