Quote Originally Posted by strelitzia View Post
Oddly, there is no category id 1049 in the database, but there is a product with master_categories_id set as 1049.

I have confirmed that ZC admin reports master_categories_id 1049 as invalid.

Do you have any idea why ZC 1.5.7c never picked this up during feed generation but ZC 2.0.0 does?
No clue, but you can backtrace the code prior to includes/classes/gpsfFeedGenerator.php(717) to see the function that's called to determine a product's category tree and compare between zc157c and zc200 to see what change(s) might have been made.