NodeJs async waterfall (callback method is not a function)

I am having a problem using async waterfall where I find that after calling the second callback (cbNumPages), the first parameter "pages" is the actual callback for the next function, instead of the last parameter "cbGetFiles" which it should be (as far as I know async waterfall says that last parameter should always be the callback, well in this case is apparently not).

The code is the following:

async.waterfall
            ([
                function(cbNumPages)
                {
                    request({
                        url: 'any-url',
                        qs: {},
                        method: 'GET',
                        headers: {
                            'Authorization' : 'any-auth'
                        }
                    }, (err, response, body) => {
                        if (!err && response.statusCode == 200)
                        {
                            var $ = cheerio.load(body);
                            var pagesList = $('ol.aui-nav').children();
                            if(pagesList.length<1)
                            {
                                var numPages = 1;
                            } else {
                                var numPages = pagesList.length-2;
                            }
                            console.log(numPages);
                            var pages = new Array(numPages),
                                total = numPages*20,
                                iterator = 0;

                            async.eachSeries(pages, function(page, cb)
                            {
                                if(page>1)
                                {
                                    pages[iterator] = iterator;
                                }else {
                                    pages[iterator] = iterator*20;
                                }
                                iterator++;
                                cb();
                            }, function(err){
                                if(err) cbNumPages(err);
                                cbNumPages(null, pages);
                            });
                        } else {
                            cbNumPages(err);
                        }
                    })
                },

                function(pages, cbGetFiles)
                {
                    var files = [];
                    var limitDate = moment().tz('Europe/Madrid').subtract(330,'days').format();

                    async.eachSeries(pages, function(page, cb)
                    {
                        request({
                            url: 'any-url'+page,
                            qs: {},
                            method: 'GET',
                            headers: {
                                'Authorization' : 'any-auth'
                            }
                        }, (err, response, body) => {
                            if(!err && response.statusCode == 200)
                            {
                                var $ = cheerio.load(body);
                                var rows = $('tr[id^=\'attachment-\']');
                                async.eachLimit(rows, 1, function(row, cb)
                                {
                                    var id = row.attribs['id'];
                                    var file = row.attribs['data-attachment-filename'];
                                    var author = $(row).children('.creator').text().trim();
                                    var created = $(row).children('.created-date').text().trim();
                                        created = moment.tz(created, 'MMM D, YYYY', 'Europe/Madrid').format();
                                    var urlFile = 'simple-file' + $(row).children('.filename-column').children('.filename').attr('href');
                                    var extension = row.attribs['data-attachment-filename'].split('.');
                                        extension = extension[extension.length-1];
                                    if(created<limitDate && validExtensions.indexOf(extension)>-1)
                                    {
                                        var f = '{ "id": "' + id + '",';
                                            f += ' "file": "' + file + '",';
                                            f += ' "url": "' + urlFile + '",';
                                            f += ' "author": "' + author + '",';
                                            f += ' "modified": "' + created + '" }';
                                        files.push(JSON.parse(f));
                                    }
                                    cb();
                                }, (err) => {
                                    if(err) cbGetFiles(err);
                                });
                                cb();
                            } else {
                                cb(err);
                            }
                        });
                    }, function(err){
                        if(err){
                            cbGetFiles(err);
                        } else {
                            cbGetFiles(null, files);
                        }
                    });
                },

                function(files, cbGetAutors)
                {
                    var filesFinal = {};
                    for(var f in files)
                    {
                        if(!filesFinal[files[f].author])
                        {
                            var ff = {};
                            for(var i in files)
                            {
                                if(files[i].author === files[f].author)
                                {
                                    ff[files[i].file] = files[i].url;
                                }
                            }
                            filesFinal[files[f].author] = ff;
                        }
                    }
                    cbGetAutors(null, JSON.parse(JSON.stringify(filesFinal)));
                },

                function(filesFinal, cbSendEmail)
                {
                    var authors = Object.keys(filesFinal);
                    async.eachSeries(authors, function(author, cb)
                    {
                        var name = author.split(' ');

                        var email = 'simple-mail@gmail.com';
                        var msg = '<p>Hi ' + author + ',</p><p>how is it going:</p><p>';
                        for(var a in Object.keys(filesFinal[author]))
                        {
                            msg += '<p style="margin-left:20px"> '+ICON_DOC+' <a href="';
                            msg += filesFinal[author][Object.keys(filesFinal[author])[a]]+'">'+Object.keys(filesFinal[author])[a]+'</a></p>';
                        }
                        msg += '</p></p><p><b>NOTE: This is a no-reply address.</b></p><p>Have a nice day! '+ICON_MONKEY+'</p>';

                        var message = {
                            text:    msg,
                            from:    'test@mail.com',
                            to:      email,
                            bcc:     '',
                            subject: 'Sample subject',
                            attachment: [{data: msg, alternative: true}]
                        };

                        serverEmail.send(message, function(err, message)
                        {
                            if(err)
                            {
                                cb(err);
                            } else {
                                console.log(message);
                                cb();
                            }
                        });

                    }, function(err){
                        if(err) cbSendEmail(err);
                        cbSendEmail();
                    });
                }

            ], (err) => {
                if(err) console.log(err);
            });

I would like to know if there is a way to control this issue or at least if there are another options for what I want to do.

Thanks.

via avilac