Modal Ajax Form Submitting Twice

There is something weird about the ajax modal that sends twice to the backend and not all users experience that. I have no idea why this problem appear suddenly.

Here’s my code:
let submit = false;

function formSubmit(that)
{
if(!submit) {
submit = true;
("form button").hide(); ("#loading-img").show();
var formData = new FormData(that);
.ajax({ url: (that).attr(‘action’),
type: (that).attr('method'), data: formData, statusCode: { 403: function(error) { (“button”).show();
("#loading-img").hide(); (".system_error").text(error.statusText);
submit = false;
},
500: function(error) {
("button").show(); ("#loading-img").hide();
(".system_error").text(error.statusText); submit = false; } }, success: function(result) { (“form button”).show();
$("#loading-img").hide();
submit = false;
},
cache: false,
contentType: false,
processData: false
}
});
}
}

('#modalForm').bind('shown.bs.modal', function(modal) { var title = (modal.relatedTarget).data(‘title’);
var uri = $(modal.relatedTarget).data(‘form-uri’);

$('.modal-header h4').text(title);

$.get(uri, function(result) {
    $('#loadBody').html(result);

    $('#loadBody form').on("submit", function(e) {
        e.preventDefault();
        e.stopPropagation();
        var that = this;
        formSubmit(that);
        return false;
    });
});

});

Has anyone ever faced this problem? Please help me