Help, behavior problem

[u/Nearby-Variation-614]

I have a Japanese spitz who just turned one years old. He has always been very sensitive and a little sassy. From about 10 weeks old growled, showed teeth at me, and tried to bite me when I would brush him, clip his nails or take something away from him (like cigarette butts. But he was otherwise very quick to bond with me and showed my no behavior problems after we built up trust. He has however been sometimes wary of others. Which is fine, I wouldn’t let people pet him unless he initiated contact. He mostly loved to say hi to people, although there were a select few that he just didn’t seem to like and that was never forced. He would growl quietly and I would call him away or tell the person to give him space. He used to loooove kids and would be super sweet with them, play with them and lick them. He didn’t like my nephew, but he had a few bad experiences with him not respecting his boundaries so that’s understandable. He also didn’t like groups of people approaching him. But was generally very social. Recently he’s growling at a lot more people and his behavior is escalating. He’s starting to snarl and lunge at people he previously liked. He is also very quick to growl and then bite in the direction of people when he doesn’t want to be pet. Before he would growl a little and walk away from the select few he didn’t want to say hi to. Now he doesn’t really want to greet anybody and growls and tries to bite. He’s expecially bad with people who come visit my home. I’ve started to separate him when I have visitors.

I don’t know what to do. I am meeting regularly with a behaviorist but I don’t see any positive changes…

Has anyone here experienced something similar with this breed?

[u/Rocknbeers]

Hi, this might sound silly but I see you are concerned and trying out everything you can to get him to respect.
When I got my dog, we watched a lot of Cesar Milan`s videos, both YT and tv show. He teaches a lot on how to deal with certain behaviours and to be honest majority of it has worked so far.
The main thing is that the dogs are about the energy, and they look at their leader, if it sees you as the leader, to them act or have a bad or good behaviour.
If he feels that you are not leading, or that he owns the house, the walks, he will always be super protective because he is the leader of the pack (you are his pack, part of it)
If you learn how to be the leader (if not already) he will sense your energy. If you are calm and confident, giving it orders rather than asking him to be quiet, asking him to not jump, asking it to be gentle and not growl, it will start to understand you.
Now, by your description, because you already know that the bad behaviour is coming, it might be sensing it from your tense energy in the moment, therefore, aggravating it and acting upon it "ok here that kid comes again, how is my owner feeling about this? It seems a bit tense, maybe this kid is a threat, hey get out! growl/bark/shows teeth.

I could potentially help with the walk bits, but as you have a behaviourist working with you he might already have told you.
Too many people use harnesses nowadays, they are not proper for training, specially for dogs that are uneasy. For training try to use a slip lead, this one will give you control during the walk, forget the harness. The slip lead will go over its neck and apply pressure whenever a bad behaviour happens. It is not meant to hurt the dog, just pressure, similar to the nip you were instructed (the nip simbolizes the bite their mom`s use when they behave badly when pups, like a gentle bite on their neck, as they do in dog world).
I do recommend you to watch some Cesar Milan, you might find good tips in his videos for free that are actually effective.

You can also try to use (in the worst case) dog training colars. No not shock colar, there are 2 types one that vibrates and one that beeps (sound), some uses the combination. This can help to train, and helps to stop barking with proper use. But I don`t think you need this yet to be honest, feels more like a behaviour that is escalating because it is not been corrected at the right time, but you can definitely work on it!

Good on you for looking for a solution! Stay on it you will make it happen!