I usually download ebooks from Anna’s Archive and transfer it to my Kindle through the service. But 1/10 times it fails, with no apparent reason. The particular ebook in question is https://annas-archive.org/md5/e310a253a9d85992129cc2b8dd351556. What’s the way out?
With Calibre you can set it up to email your kindle email address as well and have it auto convert anything that isn’t kindle format to kindle format