Работа с асинхронными задачами в Gulp 4

Question

Я обновил gulp до версии 4.0.0, прочитал инструкцию https://github.com/gulpjs/gulp/tree/master/docs/getting-started и полностью переписал код.

'use strict';

const { series, 
        parallel, 
        src, 
        dest, 
        watch }    = require('gulp'),
      sass         = require('gulp-sass'),
      autoprefixer = require('gulp-autoprefixer'),
      gcmq         = require('gulp-group-css-media-queries'),
      sourcemaps   = require('gulp-sourcemaps'),
      notify       = require('gulp-notify'),
      gutil        = require('gulp-util'),
      ftp          = require('vinyl-ftp'),
      cleanCSS     = require('gulp-clean-css'),
      rename       = require('gulp-rename'),
      uglify       = require('gulp-uglify'),
      concat       = require('gulp-concat'),
      del          = require('del'),
      csscomb      = require('gulp-csscomb'),
      changed      = require('gulp-changed'),
      gulpif       = require('gulp-if');

function comb () {
  return src(path.scss.files)
    .pipe(csscomb('.csscomb.json')
      .on("error", notify.onError(function (error) {
        return "File: " + error.message;
      })))
    .pipe(dest(path.scss.combFolder)
      .on('end', () => { if(true) console.log('   ---------------   completed COMB'); }));
}

function combUpdate () {
  return src(path.scss.combFiles)
    .pipe(dest(path.scss.folder)
      .on('end', () => { if(true) console.log('   ---------------   updated COMB -> SCSS'); }));
}

function scss () {
  return src(path.scss.combFiles)
    .pipe(sourcemaps.init())
    .pipe(csscomb('.csscomb.json')
      .on("error", notify.onError(function (error) {
      return "File: " + error.message;
    })))
    .pipe(sass()
      .on("error", notify.onError(function (error) {
        return "File: " + error.message;
      })))
    .pipe(gcmq())
    .pipe(autoprefixer({ browsers: ['last 5 versions', '> 1%'], cascade: true }))
    .pipe(notify({ message: 'Compiled!', sound: false }))
    .pipe(sourcemaps.write('./'))
    .pipe(dest(path.css.folder)
      .on('end', () => { if(true) console.log('   ---------------   completed SCSS'); }));
}

function mincss () {
  return src([path.css.files,
      '!' + path.css.filesMin,
      '!' + path.css.folder + '**/font-awesome.css',
      '!' + path.css.folder + '**/normalize.css'
    ])
    .pipe(cleanCSS({ specialComments: 'false' }))
    .pipe(rename({ suffix: '.min' }))
    .pipe(dest(path.css.folder)
      .on('end', () => { if(true) console.log('   ---------------   completed MINIFY (.min.css)'); }));
}

function minjs () {
  return src([path.js.files, '!' + path.js.filesMin])
    .pipe(uglify())
    .pipe(rename({ suffix: '.min' }))
    .pipe(dest(path.js.folder)
      .on('end', () => { if(true) console.log('   ---------------   completed UGLIFY (.min.js)'); }));
}

function processBuild (srcUrl, baseUrl, destUrl, newest) {
  return src(srcUrl)
    .pipe(gulpif(newest, changed(path.tmp.temp + baseUrl)))
    .pipe(dest(destUrl + baseUrl));
}

function setBuild (destUrl, newest) {
  processBuild(path.css.files,    path.css.folder,    destUrl, newest); /*CSS*/
  processBuild(path.css.mapFiles, path.css.mapFolder, destUrl, newest); /*MAP*/
  processBuild(path.html.files,   path.html.folder,   destUrl, newest); /*HTML*/
  processBuild(path.js.files,     path.js.folder,     destUrl, newest); /*JS*/
  return Promise.resolve('finished');
}

function tempBuild () { return setBuild(path.tmp.temp, false); }
function distBuild () { return setBuild(path.tmp.dist, false); }
function upldBuild (cb) {
  setBuild(path.tmp.upld, true);
  return Promise.resolve('finished');
  cb();
}
function cleanTemp () { return del(path.tmp.temp, {force: true}); };
function cleanDist () { return del(path.tmp.dist, {force: true}); };
function cleanUpld () { return del(path.tmp.upld, {force: true}); }

function watchFiles() {
  watch(path.scss.files, 
        series(comb, scss, mincss, 
          cleanUpld, upldBuild, cleanDist, distBuild, cleanTemp, tempBuild));
  watch([path.js.files, '!' + path.js.filesMin], 
        series(minjs, 
          cleanUpld, upldBuild, cleanDist, distBuild, cleanTemp, tempBuild));
  watch(path.html.files, 
    series(cleanUpld, upldBuild,
          delay, upload2mbc,
          cleanDist, distBuild, cleanTemp, tempBuild));
}

function delay (done) {
  setTimeout(done, 100);
}

function upload2mbc() {
  var upload = [path.tmp.upld + '**/*.*'];
  return src( upload, { base: '', buffer: false } )
    .pipe(conn.newer('/public_html/ext' ))
    .pipe(conn.dest('/public_html/ext' )
      .on('end', () => { if (true) console.log('   ---------------   completed FILES UPLOADED'); }));
}

exports.default = watchFiles;

exports.upload = upload2mbc;

exports.updateSass = series(comb, combUpdate);

upload2mbc ничего не отправляет на сервер, потому что upldBuild не успел собрать папку.http://prntscr.com/l8fi9g

    watch(path.html.files, 
    series(cleanUpld, upldBuild,
          upload2mbc,
          cleanDist, distBuild, cleanTemp, tempBuild));

, если я запускаю обе задачи по отдельности - все работает.http://prntscr.com/l8fimr

function upldBuild () {
  setBuild(path.tmp.upld, true);
  return Promise.resolve('finished');
}

function upldBuild (cb) {
  return  setBuild(path.tmp.upld, true);
  cb();
}

Я уже выкопал много материала, но до сих пор не могу понять, где моя ошибка.Заранее благодарим за помощь.