I modified the cover for an epub and tried to use Modify Epub to update the cover.
Spoiler:
calibre, version 5.7.2
ERROR: Modify ePub failed: No ePub files were updated
Modifying: C:\Users\David\AppData\Local\Temp\calibre_x_x6my6u \fuo6ugad_modify_epub\10364.epub
Updating metadata and cover
Parsing xml file: OEBPS/content.opf
Looking for Adobe xpgt files and links to remove
Looking for pagemaps
Looking for Google Play pagemaps
Looking for Adobe DRM meta tags to remove
Looking for all jackets
Looking for inline javascript blocks to remove
Looking for .js files to remove
Applying smarten punctuation
Smartened punctuation in: OEBPS/Text/Section0001.xhtml
Stripping Kobo remnants
Looking for files to remove: ['iTunesMetadata.plist', 'iTunesArtwork']
Looking for files to remove: ['META-INF/calibre_bookmarks.txt']
Looking for files to remove: ['.DS_Store', 'thumbs.db']
Looking for unused images
Removing unused image: OEBPS/cover.jpeg
Stripping spans
Insert or replace cover
...Looking for guide cover reference
Found guide cover reference to: Text/titlepage.xhtml
Related manifest item id: titlepage
...Looking for meta cover
Found meta tag with cover id: cover
Meta item removed: cover
...Looking for other.ms-* guide references to clean out
...Working with possible existing cover: Text/titlepage.xhtml
Guide reference removed: Text/titlepage.xhtml
...Looking for TOC navpoint for this cover
Cooper & Amelia’s First Christmas - ERROR: Traceback (most recent call last):
File "calibre_plugins.modify_epub.modify", line 78, in process_book
File "calibre_plugins.modify_epub.modify", line 204, in _process_book
File "calibre_plugins.modify_epub.modify", line 897, in _insert_replace_cover
File "calibre_plugins.modify_epub.covers", line 59, in insert_or_replace_cover
File "calibre_plugins.modify_epub.covers", line 141, in _get_and_clean_existing_cover_item
File "calibre_plugins.modify_epub.container", line 308, in get_toc_navpoint_content
AttributeError: 'NoneType' object has no attribute 'xpath'
ePub not changed after 0.09 seconds