The Smashwords Meatgrinder conversion engine performs a lot of magic behind the scenes to automatically correct many EPUBCHECK errors, though we're unable to correct them all. (smashwords.com)
One author volunteered that they'd heard such horror stories of Meatgrinder from their publisher that they kept their books off of Smashwords for that reason. (eoinpurcellsblog.com)
Smashwords is well known for Meatgrinder, its automated conversion platform. (selfpublishingreview.com)