[lumpynose]

Something about write and KeyError at the bottom of the log file.

Edit: unchecking "Remove unmanifested files from ePub" gets rid of this error and it finishes successfully.

Spoiler:

calibre, version 3.45.2
ERROR: Modify ePub failed: No ePub files were updated

Modify ePubs
Logfile for book ID 7325 (Roy Blakeley in the Haunted Camp / Percy Keese Fitzhugh)
7325
Modifying: d:\tmp\calibre_akzdsd\hhv1nx_modify_epub\7325.epub
Updating metadata and cover
Parsing xml file: OEBPS/content.opf
Parsing xml file: OEBPS/toc.ncx
Looking for files to remove: [u'iTunesMetadata.plist', u'iTunesArtwork']
Looking for files to remove: [u'META-INF/calibre_bookmarks.txt']
Looking for files to remove: [u'.DS_Store', u'thumbs.db']
Looking for unused images
Removing unused image: OEBPS/OEBPS/cover.jpg
Manifest item removed: OEBPS/cover.jpg (cover)
Changing playOrder from: 8 to: 3
Changing playOrder from: 17 to: 4
Changing playOrder from: 30 to: 5
Changing playOrder from: 35 to: 6
Changing playOrder from: 42 to: 7
Changing playOrder from: 51 to: 8
Changing playOrder from: 57 to: 9
Changing playOrder from: 63 to: 10
Changing playOrder from: 72 to: 11
Changing playOrder from: 80 to: 12
Changing playOrder from: 84 to: 13
Changing playOrder from: 92 to: 14
Changing playOrder from: 100 to: 15
Changing playOrder from: 108 to: 16
Changing playOrder from: 113 to: 17
Changing playOrder from: 116 to: 18
Changing playOrder from: 121 to: 19
Changing playOrder from: 127 to: 20
Changing playOrder from: 134 to: 21
Changing playOrder from: 141 to: 22
Changing playOrder from: 148 to: 23
Changing playOrder from: 156 to: 24
Changing playOrder from: 160 to: 25
Changing playOrder from: 166 to: 26
Changing playOrder from: 172 to: 27
Changing playOrder from: 182 to: 28
Changing playOrder from: 192 to: 29
Changing playOrder from: 201 to: 30
Changing playOrder from: 205 to: 31
Changing playOrder from: 213 to: 32
Changing playOrder from: 219 to: 33
Changing playOrder from: 227 to: 34
Changing playOrder from: 236 to: 35
Stripping spans
Stripped spans in: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
Stripped spans in: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-1.htm.html
Stripped spans in: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
Stripped spans in: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-4.htm.html
Stripped spans in: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-0.htm.html
Stripping Kobo remnants
Looking for redundant entries in manifest
Looking for unmanifested files
Found file to to remove: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
Found file to to remove: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-1.htm.html
Found file to to remove: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
Found file to to remove: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-5.htm.html
Found file to to remove: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-4.htm.html
Found file to to remove: OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-0.htm.html
Looking for broken links in the NCX
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-0.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-0.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-0.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-0.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-0.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-0.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-1.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-1.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-1.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-1.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-1.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-1.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-1.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-2.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-4.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-4.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-4.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-4.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-4.htm.html
TOC Navpoint broken to remove of: @public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-4.htm.html
Looking for Adobe xpgt files and links to remove
Looking for Adobe DRM meta tags to remove
Looking for CSS margins
Modified CSS margins in: OEBPS/pgepub.css
Modified CSS margins in: OEBPS/1.css
Modified CSS margins in: OEBPS/0.css
Looking for extra CSS to append
Modified CSS margins in: OEBPS/pgepub.css
Modified CSS margins in: OEBPS/1.css
Modified CSS margins in: OEBPS/0.css
Looking for inline javascript blocks to remove
Looking for .js files to remove
Applying smarten punctuation
Roy Blakeley in the Haunted Camp - ERROR: Traceback (most recent call last):
File "calibre_plugins.modify_epub.modify", line 81, in process_book
File "calibre_plugins.modify_epub.container", line 680, in write
KeyError: u'OEBPS/@public@vhost@g@gutenberg@html@files@31452@31452-h@31452-h-3.htm.html'

ePub not changed after 0.38 seconds

Edit: unchecking "Remove unmanifested files from ePub" gets rid of this error and it finishes successfully.