How old is Thore? I love his name by the way!
I may be wrong, but this is just my opinion. You mentioned that he does this while he is peaceful in his crate. I believe that a dog also needs his own space and private time just like we do and I think it's great that he actually likes his crate and feels safe in it. Do you adjust him or his toys while he's in his crate? Or is he just asleep on the sofa or somewhere in the open? If he's out in the open, there is definitely no excuse for the growling there. I agree that your dog should
never growl at you in a defensive way, but if he's in his quiet space and resting and someone or something comes to break that peace constantly, that could explain why this has started. I learned this the hard way. When I was a teenager, I had a dog that I loved so much that I just couldn't leave her alone and she hated me. She always slept with my dad because he didn't bother her. I, on the other hand, couldn't stop touching her or kissing her
especially when she was asleep. Maybe this doesn't relate to you at all!!
I just know that I have a tendency to be like "Elmira"...LOL!!