We adopted an 8 week old rescue dog nearly 3 years ago. She's a ridgeback / staffy mix, now 30kgs. I did puppy training with her and she is very high energy, loves to play a lot.
When she was a year old, she had some sort of bad experience in kennels (she was already going there for daycare once a week and had stayed before). She nipped at one of the workers there and would only let certain people take her from her crate to play. We called in a behaviourist who had worked with that particular kennel before and with some pointers and training she started going back there for daycare. She had a certain amount of time outs though as she was showing mild aggression towards other dogs. We stopped daycare and started avoiding certain situations (crossing the road when we saw other dogs etc).
Since then, she has snapped at a couple of people in our house (hands moving quickly near her as people speak, never anything directed towards her). She has made contact but never left a mark or caused pain. She has never shown any aggression towards me, dh or any of the dcs. When guests come, unless they are super comfortable with her, we crate ddog.
Last year we got a puppy (chi / maltese rescue) and they get along fine after a rocky start. We thought that maybe another dog would help her.
We also found a great dogsitter this year who is a very good trainer and keeps dogs in his house for boarding. Both dogs passed the evaluation test and stayed for 2 nights. They have just boarded again for 4 nights and when I collected them yesterday, the trainer said that our first dog attacked another very docile dog and snapped at his wife and his child. He put them through their temperament evaluations again and they both failed more than once. Little dog is mirroring big dog's behaviour. Obviously they can't go back. He suggested training and some strategies to make ddog less nervous but I really don't know where to go from here.
I am in bits typing this, please don't flame me, are there any solutions out there?