I bred a show champion. She was so beautiful that I repeated the mating and kept the best bitch puppy from the resulting litter. At eight weeks when I sold the litter all mouths were perfect. However at six months the mouth of the puppy that I had kept had become undershot with the eruption of the permanent teeth.
I sold her cheaply as a pet and her owner still tells me twenty five years later what a wonderful little dog she was.
I don't think that a breeder can be blamed when the second teeth come in "wrongly" at about five months, unless one of the puppy's parents are undershot.
However I do think that this is an issue that is open for discussion. There is a huge difference between a dog with a badly undershot jaw, and the case of a dog with level jaws where say a couple of teeth on the bottom jaw protrude forward, so that there is not a perfect scissor bite.
Unfortunately cockers are a popular breed with large classes in the showring. It is too easy for judges to eliminate dogs for mouth faults because a dog either has a perfect mouth or it has not. There is no matter of opinion, like whether a dog is too short or too long, has well laid shoulders or whether the shoulders are too upright, or whether a dog has moved correctly or not. Different judges see construction and movement differently and they judge on matters of degree. But if a dog doesn't have a scissor bite even if the jaw is correct, but the teeth are slightly misplaced, then in most cases the dog will be penalised, if not eliminated.
This is most strange because we don't always do this with people. I find the face of Susan George say, with her less than perfect teeth, enormously more pleasing than those Hollywood starlets with perfect eyes, noses and mouths. They all look so bland! A small degree of imperfection gives individuality and seems to enhance the attraction!
John