ePub might be missing files in manifest [was #33078]
Some TEI files (e.g., https://raw.githubusercontent.com/COST-ELTeC/ELTeC-eng/master/level1/ENG18400_Trollope.xml) will have a broken opf manifest: the manifest and spine sections only reference the front matter, while the guide contains all files. As a consequence, the EPUB appears empty.
The problem appears to be in epub.xsl:1034ff and to be there since at least f668bf18 which is very long ago … the code is probably there for a reason, so we need to check for regressions.