Require.js - order of loading libraries?

Question

Im trying to make Single Page Application (with Knockout.js - it's necessary to use it) which imitates products page in online shop. Here's how it looks like (for better understanding):

main page

Im using require.js, knockout.js and underscore.js for filtering items by price. The problem is - sometimes im getting error that _.filter is not a function. Here's my Sidebar ViewModel file:

define(
    ['jquery', 'underscore', 'knockout',  'core/get_product_list', 'core/read_set_data', 'text!view-model/sidebar/sidebar.tmpl'],

    function ($, _, ko, getProductList, ReadSetData, sidebarTemplate) {
        var SidebarViewModel = function (options) {
            //Variables
            var self = this;
            self.sidebarElement = options.sidebarElement;
            self.currentProductsPerPage = ReadSetData.currentProductsPerPage;
            self.pageNumber = ReadSetData.pageNumber;
            self.items = ReadSetData.items();
            self.itemsTotal = ko.computed(function () {
                return self.items.length;
            });
            self.filterPrice = ko.observableArray();

            //Applying template
            self.sidebarElement.html(sidebarTemplate);

            //Filtering by price using Underscore
            self.applyPriceFilter = ko.computed(function(){
                if (self.filterPrice().length !== 0) {
                    var minValue, maxValue;

                    $.each(self.filterPrice(), function() {
                        var min = Number(this.split('-')[0]),
                                max = Number(this.split('-')[1]);

                        if (!minValue && !maxValue) {
                            minValue = min;
                            maxValue = max;
                        }
                        if (minValue > min) minValue = min;
                        if (maxValue < max) maxValue = max;
                    });
                        var filterItems = _.filter(self.items, function(item) {
                            return (item.price() > minValue && item.price() < maxValue);
                        });
                            ReadSetData.pageNumber(0);
                            ReadSetData.items(filterItems);
                        }
                        else
                        {
                            ReadSetData.pageNumber(0);
                            ReadSetData.items(self.items);
                        }
            });
        };
        return SidebarViewModel;
    });

It's filtering by price as expected, but if i refresh page few times - im getting this error:

error image

If i refresh a page again, this error dissapears and filtering working fine again. It seems like underscore.js doesn't loading and that's the reason of an error (as i think).

Here's my require.config:

require.config({
paths: {
    text: '../libs/text/text',
    jquery: '../libs/jquery/jquery-min',
    popper: '../libs/popper/popper-min',
    underscore: '../libs/underscore/underscore',
    knockout: '../libs/knockout/knockout',
    bootstrap: '../libs/bootstrap-grid/bootstrap',
    material_design: '../libs/material-design/mdb'
},
shim: {
    jquery: {
        exports: '$'
    },
    underscore: {
        exports: '_'
    },
    material_design: {
        deps: ['jquery']
    }
}
});


require(['jquery', 'popper', 'bootstrap', 'knockout', 'material_design', 'main'], function(
    $,
    popper,
    bootstrap,
    ko,
    Material_design,
    MainViewModel
) {
var mainContent = $('#main'); //keep a reference to the root element

//  ---------------------------------------------
//  Applying bind of the MainViewModel
//  ---------------------------------------------
ko.applyBindings(
        new MainViewModel({
            element: mainContent
        }),
        mainContent[0]
);
});

What am i doing wrong? Maybe i wrote something in wrong order? Or any ideas what can be wrong? Thanks!