[Exist-open] Bug? KWIC fulltext (ft:query) doesn't work if variable in path was "tagged" in preceding "return".

[AG <gru...@gm...>]

     First of all, Hello everybody!
     I'm new here and very excited to be on this list!
     Here is my problem. After reading XQuery and eXist-db documentations,
I can't figure it out, so I decided to ask the question here.

*In a nutshell:* The fulltext search with KWIC doesn't work if the variable
in the path for fulltext search was put in a tag in preceding "result". It
returns an empty result.

*Explanations: *

*XML file*

> <root>
>     <node>blablabla</node>
>     <node>blab KEYWORD labla</node>
>     <node>blablabla</node></root>
>
> *Index configuration (collection.xconf)*

> <collection xmlns="http://exist-db.org/collection-config/1.0">
>     <index xmlns:xs="http://www.w3.org/2001/XMLSchema">
>         <lucene>
>             <text qname="root"/>
>             <text qname="node"/>
>         </lucene>
>     </index></collection>
>
> *XQuery without "tagged" result (it works)* *(look at "return $node")*

> let $my_texts :=
>     for $node in collection("path_to_my_collection")//node
>     return
>         $node
>
> for $my_hit in $my_texts[ft:query(., "KEYWORD")]
> return
>     $my_hit
>
> The Xquery code above works and I get a result.

> 1<node>blab KEYWORD labla</node>
>
> But it doesn't work when the first result on which fulltext search is
launched was put in a tag. (My whole query is more complex and I need to
put this result in the tag to use it in another place of my code.)

*XQuery with "tagged" result (it doesn't work)* *(look at "return
<tag>{$node}</tag>")*

> let $my_texts :=
>     for $node in collection("path_to_my_collection")//node
>     return
>         <tag>{$node}</tag>
>
> for $my_hit in $my_texts[ft:query(., "KEYWORD")]
> return
>     $my_hit
>
> This query return 0 result.

When I debug like this:

*XQuery for debugging*

> let $my_texts :=
>     for $node in collection("path_to_my_collection")//node
>     return
>         <tag>{$node}</tag>
>
> return
>     $my_texts
>
> I get this:

> 1<tag>
>     <node>blablabla</node></tag>
>
> 2<tag>
>     <node>blab KEYWORD labla</node></tag>
>
> 3<tag>
>     <node>blablabla</node></tag>
>
> What I tried:

   - different path combinations: $my_texts/tag[ft:query(.,
"KEYWORD")], $my_texts/tag/node[ft:query(.,
   "KEYWORD")], $my_texts/*[ft:query(., "KEYWORD")],
$my_texts/tag//*[ft:query(.,
   "KEYWORD")], $my_texts//*//*[ft:query(., "KEYWORD")] etc...
   - add <tag> in the Index configuration (<text qname="tag"/>)

What I missed? Or it is an eXist-db bug? (my eXist version: 4.7.0)
Many thanks in advance for all your help!
Sincerely, AG.