not really knowledgeable on this, but my take is...if you have a long time breeder and they have had to replace a puppy 3x during their breeding during a 12 year span.I would not find that totally abnormal. They are essentially playing with genetics trying to keep the breed healthy, and in conformity to breed standards. For instance a particular stud dog had one bad trait , aggressiveness..you learned from your breeding program that he passed this trait on , but overall his conformation was perfect. You then bred him to more laid back bitches and found that you were no longer seeing this behavior, A generation or two later one of his puppies were bred and although you hand's seen this in years you suddenly have a puppy with this flaw. I think things like this can happen in breeding and while reputable breeders try to avoid this it can occur. I don't think they need to explain it to the average buyer as it becomes complicated when your talking genes and how to breed certain characteristics in or out of your line. The fact that the breeder stands up to her contract is what would be meaningful to me. Thats my take on the subject...