The first full scan logged "Invalid data found when processing input" per file and carried on. That line is about the file: the scanner skips it, so the book never appears in the library at all. Census of the 43 refused files: 38 were 0 bytes, 3 held WAV bytes behind a .mp3 name, 2 were unreadable. The check to run first is a byte count, not a server investigation. Full suite: 818 tests, exit 0.