DSpace uses Apache Solr under the hood and directly queries it. DSpace copies all of its fields into a search_text field which is very likely to include both Jaume Melendres, and Melendres, Jaume. See
here,
here, then
the field type. The field type is responsible for the indexing behaviour (type="index"), and the search behaviour (type="query"), which both use
analyzers to define their behaviour. DSpace uses the
Lucene query parser which is the part that gives meaning to the double quotes.
So, what data do you have in the search_text field?
Try modifying the schema.xml file, restarting DSpace, and re-indexing, to see how it affects the search queries in both the frontend and the Apache Solr backend. That will help give you an idea of how the search works and doesn't work.