The entry in the table at the beginning of section 4 (file main-driver.odd, circa line 968) says:
<row>
<cell>├</cell>
<cell><gi>facsimile</gi></cell>
<cell>The <gi>facsimile</gi> defines sets of images that correspond
with the text. This element should only be used if page images are
included and if this particular mechanism for linking page images is
chosen. See <ref target="#Linking">between encoded text and images
of source documents|Linking between encoded text and images of
source documents</ref>.</cell>
</row>
There is no element with ID "Linking"
The content of the <ref> is clearly messed up, too.
The entry in the table at the beginning of section 4 (file main-driver.odd, circa line 968) says:
<ref>
is clearly messed up, too.