Even weirder. I went to scramble the split
output (using scramble plugin) book
and
Code:
calibre, version 7.5.1
ERROR: ScrambleEbook [v0.6.0]: Source ebook must be de-DRM'd and in one of these formats:
- azw3
- epub
- kepub
- kepub.epub.
Please select another.
I can View the (split) book in Calibre.
It does split. Just fails the font (shows red shield until I added the encryption.xhtml), then it fails to load in the editor the next time
I just ran Scramble on the full Calibre Converted to EPUB (from AZW3) and that ran.

I will attach the scrambled source. Let me know, and I (or you can) remove it after you have grabbed it
Moderator Notice
attached epub removed as requested -- Jimm