Gulp Clear Appears to Not Always Remove File(s) or Folder(s) During Multi-Source Merge

Question

I wrote a quick gulp task that merges several sources. It starts by clearing out the existing JS build folder of everything, then it builds the AngularJS template cache, and finally minifies and concats the files for use in the application, but 3 out of 4 times that gulp is run it throws an error indicating a file or folder already exists during build:

$ gulp compress
[13:29:52] Using gulpfile D:\projects\app\mobile\gulpfile.js
[13:29:52] Starting 'compress'...
stream.js:74
      throw er; // Unhandled stream error in pipe.
      ^

Error: EEXIST: file already exists, mkdir 'D:\projects\app\mobile\www\js\components'
    at Error (native)

But the clear should have removed all the files and folders prior to this sub task running:

gulp.task('compress', function (done) {

    // Clear existing build files
    var clear = gulp.src('./www/js/**/*')
        .pipe(vinylPaths(del));

    // Build the template cache
    var cache = gulp.src('./www/templates/**/*.tpl.html')
        .pipe(templateCache('app-templates.js', {
            root: 'templates',
            transformUrl: function (url) {
                return url.replace(/\.tpl\.html$/, '.html')
            }
        }))
        .pipe(gulp.dest('./www/js'))

    // Minify and concatenate the application
    var build = gulp.src('./src/**/*.js')
        .pipe(uglify({
            mangle: false
        }))
        .pipe(gulp.dest('./www/js'))
        .pipe(concat('app.min.js'))
        .pipe(gulp.dest('./www/js/build'));

    // Merge multiple sources into a single task
    return merge(clear, cache, build);
});

Any ideas what I've missed? Or is there a better way to do this type of task? Appears to work great other than it not clearing away the old build.