A lot of breeders make excuses for them, they played with the other puppies, don't rub the ears, don't let them get a crease, if they have an ear infection, etc.
But it is a disqualifying fault. I think it is genetic. Not all litters are uniform. Some will have thicker heavier ears, and some of those might not go up. You can usually train them up by gluing or taping if you do it soon enough, but you shouldn't have to monkey around with the ears.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC