Since I'm having connection issue Kobo <--> macOS and just don't want to restart my laptop or play with cables/type-c hubs each time - I got KOreader installed on my Clara BW in order to use its wireless sync feature with my Calibre library. After loading books some of them had no covers but I was able to resolve that by long pressing on book and selecting "Refresh cached book information".
The main problem I'm facing is one of my books can't be opened (as I thought before). It just hangs and you need to reboot device. To debug that I exported the book from Calibre and realized that it also hangs there while showing "Copying files and writing metadata...". It takes roughly 5-7 min. to finish the process. When doing export of EPUB only - it's blazing fast.
So I tried to go further and check books md5s (per thread where people were complaining about wireless connection to Calibre results in broken files), that was a dead end since md5 of epub saved from Calibre and one that Calibre pushes to device are different. And looks like it's not only true for that particular book. Idk, maybe different filesystems on host OS and device might make that discrapancy.
As final test I installed and used epubcheck tool to validate epub file, here's what I've got:
Code:
epubcheck 11_22_63\ S\ King\ \(93\).epub
Validating using EPUB version 2.0.1 rules.
ERROR(NCX-001): 11_22_63\ S\ King\ \(93\).epub/OEBPS/toc.ncx(-1,-1): NCX identifier ("FB2BookID") does not match OPF identifier ("urn:uuid:cc321c08-44af-4ecb-82eb-1b95cb3715db").
Check finished with errors
Messages: 0 fatals / 1 error / 0 warnings / 0 infos
EPUBCheck completed
But another book from the same author/vendor has that error +1 more and works just fine.
So on my last try I didn't want to restart the device and just left it, not sure how long it took but the book was finally opened.
Any advice on what else I can check/tweak? Because Calibre epub viewer/editor opens it, Books app can read it without any issues - I'm running out of ideas what to check next.