Images do not extract to epub OPF manifest

I am transforming 
a DB5 (1.76) book to epub using oXygen 12.2, and running epubcheck gives me 
a warning that images are not declared in the OPF file. Inexpicably, I do 
get only one image showing in the manifest:

"<manifest>

        <item id="ncxtoc" 
media-type="application/x-dtbncx+xml" href="toc.ncx" />

        <item media-type="text/css" 
id="css" href="../epub3.css" />

        <item id="cover" 
href="cover.html" media-type="application/xhtml+xml" />

        <item id="coverimage" 
href="images/frontcover.jpg" media-type="image/jpeg" />

        <item id="d0e274" 
href="pr01.html" media-type="application/xhtml+xml" />

        <item id="d0e306" 
href="chap1.html" media-type="application/xhtml+xml" />

        <item id="d0e350" 
href="sec1.2.html" media-type="application/xhtml+xml" />

        <item id="d0e403" 
href="sec1.3.html" media-type="application/xhtml+xml" />

        <item id="d0e424" 
href="chap2.html" media-type="application/xhtml+xml" />

        <item id="d0e451" 
href="images/Figure2-1.gif" media-type="image/gif" />

        <item id="d0e715" 
href="sec2.2.html" media-type="application/xhtml+xml" />

 ....."

 

I've checked the XML markup, and 
every image in each chunk has the imagedata file format declared as GIF, 
e.g.:

"<figure pgwide="1" xml:id="fig2.2" 
floatstyle="before">

            
<title>Australia’s meso-scale marine bioregions. Source: Department 
of Environment,

                
Water, Heritage and the Arts.</title>

            
<titleabbrev>Australia’s meso-scale marine 
bioregions</titleabbrev>

            
<mediaobject>

                
<textobject>

                    
<phrase>Australia’s meso-scale marine bioregions</phrase>

                
</textobject>

                
<imageobject role="fo">

                    
<imagedata fileref="images/Figure2-2.gif" width="70%" align="center"

                        
format="GIF" />

                
</imageobject>

                
<imageobject role="html">

                    
<imagedata fileref="images/Figure2-2.gif" width="450px" align="center"

                        
format="GIF" />

                
</imageobject>

            
</mediaobject>
        
</figure>" 

 

I can't see what markup 
I'm missing to get images to extract to the OPF. Any help appreciated 
thanks.

 

Dave Gardiner