Failed to compile with 0 errors / inconsistent builds - symfony

Question

I'm trying to move from Assetic to Webpack but it seems quite tricky.
I have 6 different JS entries, containing different files.
I'm running "yarn encore dev":
Problem 1: I get "ERROR Failed to compile with 0 errors" - BUT it does seem to compile.
Problem 2: All compiled entries are almost identical (same size) except the first one. All that change is the filename written inside the file.
Maybe it's not really compiling in fact, then how could I fix the "Failed to compile with 0 errors" error?
My webpack.config.js:
let Encore = require('#symfony/webpack-encore');
Encore
.setOutputPath('web/build/')
.setPublicPath('/build')
.setManifestKeyPrefix('build/')
//-- this one is well-compiled (I think)
.addEntry('app-vendors', './assets/app-vendors.js')
//-- those ones are all identical
.addEntry('app-classes', './assets/app-classes.js')
.addEntry('markable-maps-classes', './assets/markable-maps-classes.js')
.addEntry('markable-maps-vendors', './assets/markable-maps-vendors.js')
.addEntry('calendar-vendors', './assets/calendar-vendors.js')
.addEntry('calendar-classes', './assets/calendar-classes.js')
.enableSingleRuntimeChunk()
;
var config = Encore.getWebpackConfig();
config.node = { fs: 'empty' };
module.exports = config;
app-classes.js
let files = [
'classes/Foldable.js',
'classes/HorizontalPlanning.js',
'classes/PlanningWorkTimes.js',
'classes/AttachmentsList.js',
'classes/CameraModal.js',
'classes/Affair.js',
'classes/AffairStepsFinancialInfos.js',
'classes/Forms.js',
'classes/NewEventContextMenu.js',
'classes/GroupAction.js',
'classes/AuthRights.js',
'functions.js',
'init.js'
];
for (let file of files)
require('../web/js/Business/' + file);
calendar-classes.js
let files = [
'classes/Calendars/BaseCalendar.js',
'classes/Calendars/SingleCalendar.js',
'classes/Calendars/SyncCalendars.js',
'classes/Calendars/EmployeesSyncCalendars.js',
'classes/Calendars/Planning.js',
'classes/Calendars/RoomsSyncCalendars.js',
];
for (let file of files)
require('../web/js/Business/' + file);
calendar-vendors.js
let files = [
'fullcalendar/fullcalendar.js',
'fullcalendar/locale/fr.js',
];
for (let file of files)
require('../web/js/Business/' + file);
Command output:
$ yarn encore dev
yarn run v1.16.0
$ '/Volumes/Macintosh HD Data/Users/theredled/Sites/qualispace/deploy/node_modules/.bin/encore' dev
Running webpack ...
ERROR Failed to compile with 0 errors 17:11:12
Entrypoint app-vendors [big] = app-vendors.css app-vendors.js
Entrypoint app-classes [big] = app-classes.js
Entrypoint markable-maps-classes [big] = markable-maps-classes.js
Entrypoint markable-maps-vendors [big] = markable-maps-vendors.js
Entrypoint calendar-vendors [big] = calendar-vendors.js
Entrypoint calendar-classes [big] = calendar-classes.js
error Command failed with exit code 2.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.