Repeated XML `NUTS` elements not creating mapping from JSON vocabulary

[schivmeister]

Environment

rmlmapper v6.2.2 (reproducible also as far back as v6.1.3 and even older)
Linux/WSL2
Java 11

Problem

Given the following kind of input XML:

<OBJECT>
  <NUTS CODE="DE"/>
  <NUTS CODE="DE8"/>
  <NUTS CODE="DE80"/>
  <NUTS CODE="DE803"/>
</OBJECT>

and the following kind of subject mapping:

tedm:nuts a rr:TriplesMap ;
    rml:logicalSource
        [
            rml:source "resources/nuts.json" ;
            rml:iterator "$.results.bindings[*]" ;
            rml:referenceFormulation ql:JSONPath
        ] ;
    rr:subjectMap
        [
            rml:reference
                "conceptURI.value" ;
        ] .

and the following kind of predicate-object mapping:

    rr:predicateObjectMap
        [
            rr:predicate epo:hasNutsCode ;
            rr:objectMap
                [
                    rr:parentTriplesMap tedm:nuts;
                    rr:joinCondition [
                        rr:child "*:NUTS/@CODE";
                        rr:parent "code.value";
                    ];
                ] ;
        ] ;

with the following kind of value mapping vocabulary in JSON format:

      {
        "code": {
          "type": "literal",
          "value": "DE803"
        },
        "conceptURI": {
          "type": "uri",
          "value": "http://data.europa.eu/nuts/code/DE803"
        }
      },

Actual

Results in no mapping created for epo:hasNutsCode.

Expected

Should result in as many instances of epo:hasNutsCode with values as there are NUTS elements with CODE values, matching terms in the given vocabulary nuts.json.

  epo:hasNutsCode <http://data.europa.eu/nuts/code/DE> ,
                  <http://data.europa.eu/nuts/code/DE8> ,
                  <http://data.europa.eu/nuts/code/DE80> ,
                  <http://data.europa.eu/nuts/code/DE803> .

Workaround

Removing all but one NUTS element results in a successful mapping of epo:hasNutsCode.

Input:

<OBJECT>
  <NUTS CODE="DE803"/>
</OBJECT>

Output:

  epo:hasNutsCode <http://data.europa.eu/nuts/code/DE803> .

MWE

rml-mwe-nuts-json.zip

Context

This was discovered while troubleshooting #226, a result reproducibility issue pertaining to the mapping of OP TED XML notices to generate RDF.

P.S: The issue described in #226 for reproduction actually is about a partial, incomplete original result, i.e. multiple values created only one mapping, which is no longer reproducible (as in turn evidenced in this ticket).

[csnyulas]

Did anyone manage to reproduce this? What could be the cause for this behavior?
Can someone confirm that this is a bug (perhaps a regression)?

[csnyulas]

Dear developers,
Is there any chance that you can look at this problem in the near future? We would like to know if this is indeed a bug, and if yes, is it going to be fixed or not.
Thank you!