Hello,
we faced similar problem but I can not tell from your description if this is your case.
In short: our problem was caused by some known bug with missing records in candlepin table, see:
The workaround depicted in the mentioned article fixed it for us, with several repositories the task failed but it could be fixed with simple renaming of the product and running the task again.
You can check if all repositories are in the candlepin table by running:
su - postgres
psql -d candlepin
SELECT product.uuid AS “Product UUID”, product.name AS “Product Name”, product.product_id, content.content_id, content.uuid, content.label, content.name, content.arches FROM cp_pool pool JOIN cp2_products product ON pool.product_uuid = product.uuid JOIN cp2_product_content pc ON product.uuid = pc.product_uuid JOIN cp2_content content ON content.uuid = pc.content_uuid ORDER BY product.name ASC;