Your select2 dropwdown doesn't look OK in modal on bootstrap (v3) maybe?

app.js

/**
 * This has to be done this way - it's fix for bootstrap modal select2 issue
 */
$('.modal select').css('width', '100%');
$('select:not(.normal)').each(function () {
    $(this).select2({
        theme: "bootstrap", // if you use https://github.com/select2/select2-bootstrap-theme
        dropdownParent: $(this).parent()
    });
});