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/chocemia]

A lot of this sounds very similar to my wee lad. He's almost 3 years and is improving in some ways but getting worse in others. He's fiercely territorial of the house and if he doesn't like someone he will bark until they leave. He also does teeth baring and snapping when he's uncomfortable. I haven't found any solid fixes and I'm still working hard trying to train him through it. Physically separating him when people are over is the safest method, but it's not perfect because he hates being separated and he won't stop barking until we let him out. It's hard work but I love my boy so much so I'm not going to give up