AJAX-技术错误

Question

I use prestashop v 1.5.6 and one module makes me a headache. I can't understand what brings up the problem since it is not appearing all the time only sometime when accessing the checkout page or when I refresh the page.

The function is:

function loadcart() {
$('#opc-right-summary-content #opc-page-loader').fadeIn();
$.ajax({
    type: 'POST',
    url: orderOpcUrl,
    async: false,
    cache: false,
    dataType: "json",
    data: 'ajx=true&method=loadcart&token=' + static_token,
    success: function (jsonData) {
        if (jsonData.hasError) {
            var errors = '';
            for (error in jsonData.errors)
            //IE6 bug fix
                if (error != 'indexOf')
                    errors += jsonData.errors[error] + "
";
            alert(errors);
        } else {
            $('.cart-container').html(jsonData.cart_bl);
            if(jsonData.err_isset){
                $('#cart_errors').html('');
                $('#cart_errors').html(jsonData.err);
                $.each(jsonData.array, function(){
                    var elem = this;
                    $('.cart_item').each(function(){
                        var id = $(this).attr('id');
                        if (strpos(id, 'product_' + elem.id_product + '_' + elem.id_product_attribute) !== false){
                            $(this).find('td').css('background-color', '#e46f61');
                        }
                    });
                });
            }
            $('#opc-right-summary-content #opc-page-loader').fadeOut();
        }
    },
    error: function (XMLHttpRequest, textStatus, errorThrown) {
        alert("TECHNICAL ERROR: unable to loal оплата 

Details:
Error thrown: " + XMLHttpRequest + "
" + 'Text status: ' + textStatus);
    }
});

}

JS popup error: TECHNICAL ERROR: unable to loal оплата details: error thrown: [object Object] Text status: error

The consule error is:

[Deprecation] Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.
send @ jquery-1.7.2.min.js:4
jquery-1.7.2.min.js Failed to load resource: the server responded with a status of 500 (Internal Server Error)
send @ jquery-1.7.2.min.js:4
POST http://-------/ru/quick-order 500 (Internal Server Error)
send @ jquery-1.7.2.min.js:4
ajax @ jquery-1.7.2.min.js:4
loadcart @ main.js:618
(anonymous) @ states.js:15
o @ jquery-1.7.2.min.js:2
fireWith @ jquery-1.7.2.min.js:2

ready @ jquery-1.7.2.min.js:2
B @ jquery-1.7.2.min.js:2

Who is guru in AJAX please give me atlist a hint why this error appears?