Interesting. I didn't realize Calibre allowed for Debug output.
I've cut and pasted the section detailing the book here.
What's odd to me is that even though both Calibre and the Kobo list the book as 100 percent Read. The Debug output seems to be showing only 99 percent. Which I have to think is where the problem stems from.
I just tried opening the book again on the Kobo and reading until the last page. That did not change the behavior.
Code:
DEBUG: 0.9 _store_bookmarks - Current book: Bluff - Jane Stanton Hitchcock
DEBUG: 0.9 _store_bookmarks - contentIds='['file:///mnt/onboard/Hitchcock, Jane Stanton/Bluff - Jane Stanton Hitchcock.epub']'
DEBUG: 0.9 _store_bookmarks - contentId='file:///mnt/onboard/Hitchcock, Jane Stanton/Bluff - Jane Stanton Hitchcock.epub'
DEBUG: 0.9 _store_bookmarks - device_status='None'
DEBUG: 0.9 _store_bookmarks - result='{'ChapterIDBookmarked': 'OEBPS/Bluff.xhtml', 'adobe_location': None, 'ReadStatus': 2, '___PercentRead': 99, 'Attribution': 'Jane Stanton Hitchcock', 'DateLastRead': '2020-10-21T13:04:20Z', 'Title': 'Bluff', 'MimeType': 'application/epub+zip', 'Rating': None, 'ContentID': 'file:///mnt/onboard/Hitchcock, Jane Stanton/Bluff - Jane Stanton Hitchcock.epub'}'
DEBUG: 0.9 _store_bookmarks - device_status= {'ChapterIDBookmarked': 'OEBPS/Bluff.xhtml', 'adobe_location': None, 'ReadStatus': 2, '___PercentRead': 99, 'Attribution': 'Jane Stanton Hitchcock', 'DateLastRead': '2020-10-21T13:04:20Z', 'Title': 'Bluff', 'MimeType': 'application/epub+zip', 'Rating': None, 'ContentID': 'file:///mnt/onboard/Hitchcock, Jane Stanton/Bluff - Jane Stanton Hitchcock.epub'}