Multiget with several ids doesn't work [Java API]

Elastic Stack Elasticsearch
1

I'm trying to execute a multiget request using Java API:

MultiGetResponse response = this.provideMultiGetRequest()
    //username is the routing key
    .add(this.user.getMe().getUser(), FollowUpActivityRepository.ELASTICSEARCH_COLLECTION, ids)
    .execute()
    .actionGet();
	
    try {
        for (MultiGetItemResponse singleResponse : response.getResponses()) {
            if (singleResponse.getResponse().isExists())
            {
                ////////////////////////////////////////
                //when ids has more 1 id to get, it never get in this block!!!
                ////////////////////////////////////////
            }
    } catch (IOException e) {
        throw new RepositorySystemException(e);
    }

However, when ids Iterable contains only one element, it works...
What am I doing wrong?