You probably need to say what FO processor you are using, but the
identifiers that you give are in error 

http://www.w3.org/TR/xsl/slice5.html#section-N8794-Property-Datatypes

says that  ref-id and friends (which have <id> datatype)
must match


     A string of characters conforming to the definition of an NCName in
     [XML Names] and is unique within the stylesheet.

"{position()}" will produce a number which isn't a valid NCName.

David

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