Multiple biblioid's extra itemref in epub3 spine

Hi all.

    

    I'm probably doing something silly but here's my problem:

    I use the docbook-xsl-ns-1.78.1/epub3/profile-chunk.xsl
    style sheet in a custom layer and call

    

    Either --stringparam  profile.condition "epub"

    or --stringparam  profile.condition "mobi"

    

    And it picks the correct biblioid below for use in either
    the epub or a second epub for kindlegen.

    

    <biblioid class="other" otherclass="mobi"
    condition="mobi">978-------7-</biblioid>

    <biblioid class="other" otherclass="epub"
    condition="epub">978-------8-</biblioid>

    <biblioid class="other" otherclass="print"
    condition="print">978--------9-</biblioid>

    

    My problems is that which ever comes second (ie "mobi" or "epub")
    adds an extra itemref to the spine in the package.opf. This gives an
    error like -

    

    
      
        

          ERROR
          OEBPS/package.opf
          62
          37
          item with id
            'id-idp1288160' not found
        

      
    
    

    I can delete these manually but I have an automated script so would
    prefer a different solution.

    My guess is my Docbook is wrong.

    

    Thanks for your help,

    

    Peter