Troubleshooting 403 Forbidden Error when Uploading PDFs via AJAX in a Spring Boot Application

I am facing an issue with uploading PDFs via AJAX in my Spring Boot application. Most PDFs are successfully uploaded, but for 1-2 specific PDFs, I encounter a 403 Forbidden error with the message POST https://develop.abc.in/parseResume 403 (Forbidden). The PDFs seem fine to me, and I’m struggling to identify the root cause of the problem. I have included the relevant code snippet for reference. Any insights or suggestions on what might be causing this issue would be greatly appreciated.

        // ajax call for Individual add  candidate resume /
        function submitIndividualSharedFileInviteCandidate() {
            var data = new FormData();
            var files = $('#individual')[0].files
            data.append('file',files[0]);
            if (!validateIndividualResumeUpload()) {
                return false;
            }else{     
                if(dummyData == "DummyData"){
                    currentactivity_dummyData = "btn_shareEmployee_uploadIndResume";
                    deleteDummyData();
                    removeDummyData="removeDummyData";
                    }
              }     


            // var data = new FormData(formdata);
            var csrf = $("input[name='_csrf']").attr("value")

            $.ajax({
                headers : {
                    "X-CSRF-TOKEN" : csrf
                },
                enctype : 'multipart/form-data',
                processData : false, // Important!
                contentType : false,
                cache : false, //this is my servlet
                crossDomain: true, // Set this option
                data : data,
                type : "POST",
                url : "./parseResume",

                success : function(result) {
                    if (result.status == "Done") {
                        current_employee_id = result.data.employeeId;
                        $('#myModal').modal('hide');
                        // $('#candidatesBlock1').empty();

                        
                    }
                    $(".tab-slider--navresumedetails li:nth-child(2)").trigger('click')
                    $(".tab-slider--navresumedetails li:nth-child(1)").css('pointer-events', 'none');
                    // $(".add_candidate_form_parent").css('height', '698px');
                    $(".add_candidate_form_parent").css('overflow', 'auto');
                    
                    getSupplierEmail()
                    
                    var obj = result.data;
                    unparsed_resumes_list = obj;
                    current_employee_id = obj.employeeId;
                    $('#userId_unparesedResume').val(obj.employeeId);
                    unparsedBulkSharedResumePreview(obj);
                    $('#btn_save_unparsedSharedBulkResumes').html('Save');

                    
                    if (result.status == "error") {
                        $('#myModal').modal('hide');
                        
                    }
                },
                error : function(result) {
                    console.log(result);
                }
            });
            }

pdf image