dgrid custom sort issue

I'm trying to override the sort logic in dgrid as suggested by kfranqueiro in this link - https://github.com/SitePen/dgrid/issues/276.

I get the data from the server in sorted order and just want to update the UI of column header. I'm doing this -

On(mygrid, 'dgrid-sort', lang.hitch( this,function(event){
    var sort = event.sort[0];
    var order = this.sort.descending ? "descending" : "ascending";
    console.log("Sort "+ this.sort.property + " in " +order+" order.");
    event.preventDefault();
    mygrid.updateSortArrow(event.sort, true);
    myFunctionToRefreshGrid();
}));
...
myFunctionToRefreshGrid: function() {
   ...//get data from server in sorted order
   var mystore = new Memory({data: sortedDataFromServer, idProperty: 'id'});
   mygrid.set("collection", mystore);
   ...
}

Memory here is "dstore/Memory". I'm using dgrid 0.4, dstore 1.1 and dojo 1.10.4

Before calling set('collection',...) I see that sortedDataFromServer is in the desired sorted order. But for some reason, the order in the grid is different. For example, when sorted in descending order, I see that the values starting with lower case appear first in descending order and then the values starting with upper case appear in sorted order. It looks like dstore is doing something more.

What could be going on? Am I doing something wrong? Is there a different/better way to do custom sorting?

Thanks,

This is how I ended up addressing the situation - As suspected, the collection/store was further sorting my data and hence the inconsistency. I customized the store (Memory) as shown below and use the custom store when setting data to my grid.

var CustomGridStore = declare([Memory],{
    sort: function (sorted) {
        sorted = [];//Prevent the collection from sorting the data
        return this.inherited(arguments);
    }
});