The key error is here:
Error(prcgen):E24011: TOC section scope is not
included in the parent chapter:Table of Contents
I'm not 100% sure what this means. Perhaps 5824-Section.xhtml seems to be causing the issue. (I'm assuming).
It's very strange that the epub file validates. This is probably an issue with Kindlegen, but there are times when Calibre is incompatible with kindle.
Probably the strangest thing to me when I examine your epub file is that toc.xhtml (on line 24) lists itself as an item in the TOC. Why is it linking to itself? That is definitely something which might confuse Kindlegen.
Kindle requires a virtual table of contents at the front of the ebook, and your toc.xhtml would normally contain links to all the chapters. This one does not do that.
Unfortunately while it is relatively easy to figure out epub issues, Kindlegen sometimes produces strange errors, and the best solution is to keep removing chapters until you get a version that works. Then try to figure out why.
Remember that with epubs you can rename them to zip files and then unzip the files to examine everything.