There is no error within the products themselves, but your feed file doesn't appear to be complete. Perhaps it is timing out before including all of the products. Add the following manually to the end of the file each time, or find out what is causing the script to not complete.
PHP Code:
</OfferCollection>
</DataFeed>
Also, check that all of your products are included (your newest additions would be at the end of the file). You can also use MAX PRODUCTS to limit the number of products included in the feed.
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