Elasticsearch won't index single characters

Well, finally my problem is deeper than I think, and linked to the "stopwords" analyzer of Elasticsearch.

I tried to add a custom analyzer like that : 

public function buildAnalysis(AnalysisBuilder $builder)
    {
        // define ASCII folding filter
        $builder->addFilter(
            'gs_stopwords',
            'stop',
            array(
                'stopwords' => '_english_'
            )
        );

        // analyzers for which to inject ASCII folding filter
        $analyzers = array(
            'gs_analyzer_string',
            'gs_analyzer_string_ngram',
            'gs_analyzer_text_ngram',
            'gs_analyzer_string_exact',
        );

        // use injector to prepend the ASCII folding filter
        $injector = new AnalysisBuilderInjector($builder);
        $injector->prependFilter('gs_stopwords', $analyzers);
    }

And also registered the analyzer, but after QRR and reindexing I still don't get the results I want, for example if I type C For Clean it should return me the record with this Analyzer, or am I wrong? 

Is there anybody of you that tried such a thing ?

Thanks in advance for your feedbacks.

Best regards,

Enes

Hi everybody,

We finally get an answer from the support team confirming that this is a bug of the version 7.16.1 of ElasticSearch : 

https://portal.sugarondemand.com/#supp_Bugs/89369

The bug description is the same as our case, so if you're running on Sugar v11.0.3 on premise, you should get this behaviour too.