I'm interested that some posters don't believe that genetic inheritance can influence a dog's behaviour, that it's all down to "bad owners".
I don't dispute the importance of environment, owner handling, life experience in the dog, eg being attacked or ill treated definitely affects a dog. I've had several rescues and foster dogs who had terrible abuse/neglect histories. Three of them were poodle crosses, the rest collie x, German shepherd, cross breed who looked like a Kelpi but who knows and more. All those dogs came good with clear, loving, calm and consistent care.
The only dog I ever had who was a real challenge was a cockerpoo. I could write the book about my life with him, from 9 weeks, when he came home from a decent breeder - to age six when tragically he was put to sleep because of a brutal inoperable tumour. When he was two my vet and the trainer I'd been working with both reassured me that I was doing well, at a time when I thought Id failed my dog. They said separately the same thing - if this dog hadn't been with you/someone like you, he would if lucky been re-homed, or more likely put to sleep. Genetics?