jquery fileDownload executing twice

Question

Our customers might have huge records and whole download process may took more than 10 minutes.

Here our purpose is show customer some error message if download took 8 minutes.

Somehow during the process, I notice another request coming from controller exactly after 5 minutes.

Jquery

        $('#Running.modal').off().on('shown.bs.modal', function () {
            $.fileDownload("accountsummary/pdfPrint", {
                httpMethod: 'POST',
                data: $(PDFPrintForm).serializeObject(),
                cookiePath: '/myCMS/',
                successCallback: function (url) {
                    $("#Running.modal").modal('hide');
                    PDFPrintForm.remove();
                },
                failCallback: function (html, url) {
                    PDFPrintForm.remove();
                    $("#Running.modal").modal('hide');
                    $("#Failed.modal").modal({show: true});

                }
            });
        })

Back-end

If hits 8 minutes

logger.info("PDF transaction history download hits {} seconds", sec);
OutputStream outputStream;
outputStream = response.getOutputStream();
outputStream.write(errorMessage.getBytes(Charset.forName("UTF-8")));
outputStream.close();
return;

Success

Cookie c = new Cookie("fileDownload", "true");
c.setPath("/");
response.addCookie(c);
response.setHeader("Content-Disposition" , "attachment; filename=\"Account Summary-Savings/Current Account Details.pdf\"");
response.setContentType("application/pdf");
response.flushBuffer();