I set 12 eggs. Eight hatched, one with the exposed spine, one with the comb deformity (his comb issue wasn't evident until he was mature), and six normal. White Faced Black Spanish. I won't keep this breed again where I'm at because I'm not set up for their needs, but they were fun to raise nonetheless.
I'm no stranger to random genetic flukes, I've had two early trimester miscarriages that were both attributed to random genetic anomalies. My husband and I are not related in any way. It just happens sometimes. It's more common than one might think.