So, this is one of the offenders (but almost every single epub locks my ADE)
https://archive.org/details/russoturkishwari01hozi
Concerning PDFs from archive.org, here is a short list (most relevant) of the threads I have consulted before posting this question:
https://www.mobileread.com/forums/sh...ht=archive.org
https://www.mobileread.com/forums/sh...ht=archive.org
The errors in calibre are many, and while some repeat across epubs ("stock" errors) a good deal are new (non-repetitive, "guests"). The book is salvageable if the PDF was rather well OCRed, mostly unfortunately not.
It's not the copyright, not the DRM, not the PDF but rather the defectuous format of the epub.