Also consider that it might be your dog training skills that are lacking, it might not just be that the dog is dumb.
Not criticising, it's just some people are a little clumsy in their training mechanics, or they do one thing in training, and then something else the rest of the time, so the dog is simply confused.
Not criticising, it's just some people are a little clumsy in their training mechanics, or they do one thing in training, and then something else the rest of the time, so the dog is simply confused.