Multiple biblioid's extra itemref in epub3 spine

[Peter Fleck <peterfleck@gmail.com>]

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