Wondered when you would show up......good to see you here.
All dogs, every single breed (and it's usually those purebred dogs that go nuts) has the ability to go 'over the edge'. Why? Because many breeders are not breeding for the right reasons...betterment of the breed. They are breeding to get puppies, puppies to sell.
My breeder, one I found at a regional dog show, actually interviewed me, while I thought I was interviewing her!!! Too funny. I wanted a little girl golden, but when the pups were born, and started growing, the breeder called me and told me she had the perfect dog for me...except it wasn't a girl. She wanted me to agree to take him because he was a bit more assertive than the other dogs. Actually, she wanted to keep him to show and breed but he had an undescended testicle which would have been a huge issue. She knew how I handled dogs, that I had had a 'stubborn' golden before..she thought it would be a good fit. And it has been. He tried to be the boss, but that doesn't go far.
My point in this probably boring story is that a good breeder looks at many things before breeding. A 'backyard' breeder looks at getting a male for their female so they can make puppies....to sell. Yes, they are purebred but who knows what the medical backgrounds are. When these 'breeders' are mating those two dogs, they aren't looking at any undesirable traits that could be passed down. So...it's going to be pretty similar to when all those English kings and queens and various royalty kept marrying family members...nothing to dilute bad traits, so madness ensued......a lot!
Same thing thing happens with dog breeding. Lots of inbreeding creates a lot of troubles within a breed. Cockers had this issue...most popular breeds do.
Also, when you buy from a good breeder, they will usually put something into the contract about taking the dog back, at any point, for any reason. I know that if my golden had an issue that made it impossible for me to keep him, his breeder would take him in a heartbeat.
I know, I know. None of this really helps the OP. But, it may help someone who is thinking about getting a dog but doesn't want to run into the same issues down the road.