MongoError 11000 cause key duplicate nodejs and mongodb

I got MongoError 11000 cause key duplicate or it should be unique as imposed in the schema. below,my schema.

var schema = new mongoose.Schema({
  make: {type: String, trim: true, required: true},
  model: {type: String, trim: true, required: true},
  year: {type: Number},
  enabled: {type: Boolean, default: false},
  range: {type: String, enum: _.values(Range)},
  premium: {type: Boolean, default: false},
  picture: {},
  status: {type: String, enum: _.values(CarModelStatus), default: CarModelStatus.DRAFT}
});

schema.index({model: 1, make: 1, year: 1}, {unique: true});

and this is my code. (I tried to catch the error and return

 const toFix = {
    'Mercedes': 'Mercedes-Benz'
  };
          console.log('Clean carModels...');


            async.forEachOfSeries(toFix, function (to, from, cb1) {
              console.log(`FixMakeForCars ${from} -> ${to}`);
              CarModel.update({'make': {$regex: S(from).trim().s, $options: 'i'}},
                {$set: {'make': to}}, {multi: true}, function (err, res) {
                  if (err) {
                              if(err.name === 'MongoError' && err.code === 11000){
                                return console.log('carModel already exist');
                              }
                              return err.code
                            }
                            cb1()
                          });
                      }, cb);

but even this way it doesn't solve it.

any suggestions please?

via Amine Haddar