It doesn't execute the fnc

Gulp v4.0.2
It works fine if operated alone inside an vinyl-paths async task but it doesn't execute the fnc if operated inside a watch called by parent tasks and finally in async mode with vinyl-paths. Even if there is no concurrency and the fnc is called one. I understand I did not pinpoint the conditions to ricreate it but I can't do better then this.

For more info:
I've tried with injectLock.cb and injectLock. stream
```
.pipe(vinylPaths(function (paths) {
console.log('Inject:', paths);
return injectLock.cb(function (cb) {
return gulp.src(config.faIcons.inject.inject)
.pipe(
inject(gulp.src(paths), {
transform: transform_async_deferred_js,
starttag: config.faIcons.inject.starttag,
endtag: config.faIcons.inject.endtag
})
)
.pipe(gulp.dest(config.faIcons.inject.dest))
});//.pipe(touch());
return Promise.resolve();
}))
```

No files or tests are named. Start by building a minimal Gulp v4 reproduction around vinylPaths inside a watched parent task, comparing injectLock.cb with injectLock.stream; done means the callback reliably executes in the reported async setup or the failure conditions are isolated and documented.

Written by the indexing model from the issue text.