I have taken an Angel IMS CC export and corrected the errors within it:
Change all \ to // in imsmanifest
Remove _about.html pages (or one could add them to the manifest)

This cartridge now validates with IMS CC Desktop tester 'cctesterV1p0p8'

Moodle refuses to import it, because it has no course title.

A sample cartridge of a silly course is attached.

IMHO, Moodle should give the course an "Untitled" title, or dig deeper into IMS specs to pull out the course title from wherever it is hiding.