How to show translations using Angular-Translate?

Angular-translate in combination with partial-loader only shows the key and not the actual translation. I’ve tried everything but can’t seem to locate the mistake. No errors are logged.

This is my code:

app.js

var app = angular.module('myapp', [
  'ngRoute',
  'appRoutes', 
  'pascalprecht.translate',
  'angularTranslate',
  'HomeCtrl'
]); 

angular.module('angularTranslate', ['pascalprecht.translate'])
  .config(function($translateProvider, $translatePartialLoaderProvider ) {
    $translateProvider.useLoader('$translatePartialLoader', {
      urlTemplate: '/languages/{lang}/{part}.json'
    });

  $translateProvider.preferredLanguage('nl');

});

So the templates are loaded from /languages/{lang}/{part}.json

HomeCtrl.js

angular.module('HomeCtrl', []).controller('HomeController', 
  function($scope, $translate, $translatePartialLoader) {

    $translatePartialLoader.addPart('home');
    $translate.refresh();

});

In Express I have this route to ensure that the files are actually returned instead of routed to Angular:

app.get('/languages/:lang/:part', function(req, res) {
 res.sendFile(req.params.lang + "https://stackoverflow.com/" + req.params.part, { root: '././languages' });
});

home.json

{
    "HOMETITLE" : "Geweldige Whatsapp gesprekken.",
}

home.html

{{ "HOMETITLE" || translate }}

And finally I have linked everything in index.html using this order:

<script src="https://stackoverflow.com/questions/31730834/libs/angular/angular.js"></script>
<script src="../libs/angular-route/angular-route.js"></script>
<script src="../libs/angular-resource/angular-resource.js"></script>
<script src="../libs/angular-translate/angular-translate.js"></script>
<script src="../libs/angular-translate-loader-partial/angular-translate-loader-partial.js"></script>

<script src="../js/controllers/HomeCtrl.js"></script>
<script src="../js/appRoutes.js"></script>
<script src="../js/index.js"></script>

So to restate my problem: only HOMETITLE is displayed instead of the correct translation. Any help is greatly appreciated!