EpubCheck RSC-005 "Missing Resource or Duplicate ID" on generated `dc:creator` ids in aligned epubs

Running the aligned output through EpubCheck reports EPUBCheck RSC-005: Missing Resource or Duplicate ID against generated contributor lines such as <dc:creator id="6r-TupcOLQv8tTuin-7dO">Name</dc:creator>. We put every epub through Daisy ACE and EpubCheck for accessibility compliance and want a clean run.

Resolution: The generated ids are nanoid-style random strings, and a random id can begin with a digit. That is legal for an HTML5 id but not for an XML Name, which must start with a letter or underscore (see the XML 1.0 production for Name), and EPUB 3 requires XML 1.0 conformance — hence the RSC-005 from EpubCheck. It is a generator bug, acknowledged as an easy fix, so upgrade once a build carrying the fix is out. In the meantime it is cosmetic for playback (readers that follow HTML5 id rules do not care), and if you need a clean EpubCheck run today you can unzip the epub and prefix the offending ids with a letter or underscore in the OPF, updating the matching refines="#..." attributes, before rezipping.