UNKNOWN error thrown by gulp watch task - gulp

Question

I'm facing a 'randomly' occurring fatal error whilst using a watch task for gulp.
General setup
I'm on Windows 10, in which I host a Debian VM using VMWare. I have a network mapping directly into the app folder on the web server. As IDE, I use Atom, where I have opened said folder. This way, I'm directly working on the web server so that my many code changes do not require a deploy step.
Error
My build task is driven by gulp. Let me first show the error I'm facing:
W:\jd5>gulp watch
[16:21:10] Using gulpfile W:\jd5\gulpfile.js
[16:21:10] Starting 'watch'...
[16:21:11] 'watch' errored after 1.35 s
[16:21:11] Error: watch W:\jd5\src\js\vendor\ UNKNOWN
at _errnoException (util.js:1022:11)
at FSWatcher.start (fs.js:1374:19)
at Object.fs.watch (fs.js:1400:11)
at Gaze._watchDir (W:\jd5\node_modules\gaze\lib\gaze.js:289:30)
at W:\jd5\node_modules\gaze\lib\gaze.js:358:10
at iterate (W:\jd5\node_modules\gaze\lib\helper.js:52:5)
at W:\jd5\node_modules\gaze\lib\helper.js:61:11
at W:\jd5\node_modules\gaze\lib\gaze.js:420:5
at iterate (W:\jd5\node_modules\gaze\lib\helper.js:52:5)
at W:\jd5\node_modules\gaze\lib\helper.js:61:11
events.js:183
throw er; // Unhandled 'error' event
^
Regarding the randomness of this error: I often face it when starting watch, but sometimes not. It's at about 50% fail rate. Sometimes I can develop an entire day without it occurring. It's a frustrating error as it completely blocks my workflow, and it only mentions "UNKNOWN".
Gulp task
This is the gulp file I currently use:
/* load plugins */
var gulp = require('gulp');
// fast libsass-based SCSS parser
var sass = require('gulp-sass');
var del = require('del');
/* note that nano has a built-in auto prefixer, which we will use */
var nano = require('gulp-cssnano');
var gzip = require('gulp-gzip');
var minify = require('gulp-minify');
var babel = require("gulp-babel");
var sourcemaps = require('gulp-sourcemaps');
/* browser definition will be used by auto prefixer */
var myBrowsers = [
'last 2 versions',
'safari >= 8'
];
/* delete previously built files */
gulp.task('clean', function(cb) {
del(['public/css/*.css', 'public/js/**/*.js'], cb);
});
/* STYLES
================================================================================
*/
/* compile SCSS styles into CSS */
gulp.task('styles', function () {
return gulp.src('src/scss/**/*.scss')
.pipe(sass().on('error', sass.logError))
.pipe(nano({
autoprefixer: {
browsers: myBrowsers,
add: true
}
}))
.pipe(gzip({
append: false
}))
.pipe(gulp.dest('public/css'));
});
/* SCRIPTS
================================================================================
*/
gulp.task('scripts', function() {
gulp.start('scripts_global', 'scripts_vendor', 'scripts_modules')
.on('error', function(err) {
console.error('Error', err.message);
});
});
/* src/js/*.js > these are global scripts. minify, gzip and move to public/js/*.js */
gulp.task('scripts_global', function() {
return gulp.src('src/js/*.js')
.pipe(minify({
ext: {
min: '.min.js'
}
}))
.pipe(gzip({
append: false
}))
.pipe(gulp.dest('public/js/'));
});
/* src/js/vendor/*.js > vendor scripts should already be minimized, so gzip and move to public/js/vendor/*.js */
gulp.task('scripts_vendor', function() {
return gulp.src('src/js/vendor/*.js')
.pipe(gzip({
append: false
}))
.pipe(gulp.dest('public/js/vendor/'));
});
/* src/js/modules/*.js > module scripts should be transpiled to systemjs compatible modules, towards public/js/modules/*.js */
gulp.task("scripts_modules", function() {
return gulp.src("src/js/modules/*.js")
.pipe(sourcemaps.init())
.pipe(babel())
.pipe(sourcemaps.write('.'))
.pipe(gzip({
append: false
}))
.pipe(gulp.dest("public/js/modules"));
});
/* default task: first clean, then run styles and scripts build tasks */
gulp.task('default', ['clean'], function() {
gulp.start('styles', 'scripts');
});
/* watch task to continuously build styles and scripts as they change in src dir */
gulp.task('watch', function() {
// watch .scss files
gulp.watch('src/scss/**/*.scss', ['styles']);
// watch .js files
gulp.watch('src/js/**/*.js', ['scripts']);
});
As the error itself provides no information on a possible cause, some speculations:
I consider it unlikely to be a permission problem on some file, because those would always fail, not just sometimes.
I am considering both Atom and this process touching files at the same time, but have no evidence for it, nor would I know how to prevent it. The process also sometimes fails with Atom not even open.
Note that running the individual tasks without watch (gulp styles, gulp scripts) works just fine, so the task themselves look OK, more likely I'm making a mistake in how they are linked up, but I don't know what it is.
I'm on Node v8.9.4. Here are the relevant parts of my package.json:
{
"name": "",
"version": "",
"description": "",
"author": "F",
"license": "",
"devDependencies": {
"babel-plugin-transform-es2015-modules-systemjs": "^6.24.1",
"babel-preset-env": "^1.7.0",
"babel-preset-es2015": "^6.24.1",
"gulp": "^3.9.1",
"gulp-babel": "^6.1.2",
"gulp-cssnano": "^2.1.3",
"gulp-gzip": "^1.4.0",
"gulp-minify": "0.0.15",
"gulp-sass": "^3.2.1",
"gulp-sourcemaps": "^2.6.0"
},
"dependencies": {
"del": "^2.2.2",
"eslint": "^4.19.1"
}
}