Apparently, then compilation-time debugging is disabled in angular (recommended in production), the directives stop working because they rely on a missing function for getting element's scope.

This only causes trouble if this kind of code is used:

.config(['$compileProvider', function ($compileProvider) {
        $compileProvider.debugInfoEnabled(false);
    }])

See:
https://github.com/codef0rmer/angular-dragdrop/blob/master/src/angular-dragdrop.js#L71
angular/angular.js#9515