Just as a followup for others tracking this, the problem is that there is a limit to how large a MOBI periodical can be, and this particular catalog hit that limit at approximately 2400 books, when the catalog was generated with Authors, Titles and Descriptions. The alternatives are to remove Descriptions, or build smaller catalogs of library subsets. This size limitation is not based upon the number of books, but upon a combination of the number of books, the included sections and the size of the Descriptions. This hard limit only applies to MOBI catalogs.
The key to identifying this failure was the following line in the Job log:
Code:
Generating MOBI index for a periodical
Failed to generate MOBI index:
G