This is EXACTLY the reason I INSIST on all animals DNA tested for ALL defects when I purchase. "Clean by pedigree" translates to me as "Too cheap to test, and really do not want to know. Plus I am hiding something...." Seems pedigrees get "mislabeled" for many different reasons (want clean pedigree, wrong straw, not AI'd vs. bull sired, neighbors bulls, want the "popular" sire, etc, etc, etc)
Again, if an animal is worth purchasing, it is worth the extra few bucks to DNA them. Just think of all of these types of disasters that could be avoided.