5 leaved clover...
Errors of symmetry frequently occur in plants and animals (Siamese twins as an extreme [but also simplistic] example).
We learn a lot from mistakes, because that shows the basic processes in a different light than in the case of success.
Mind you, in 44 years of life and 30+ years of active Christmas nut consumption I've never seen a 3 or 5 lobed walnut or pecan.
Maybe you handle more, or have a higher incidence????
Eventually, a high incidence of "errors" becomes a new norm. If it helps survival, that's evolution... ...