Too much inbreeding in some kennels.
I had a long haired too. He only bit when someone from the family was harmed. He knew his property boundaries, slept on the ground with his tail over his nose in the snow and only took shelter in the rain. If someone he didn't know came in the yard, he was all teeth if you stepped off the walk.
The two I have on the farm are the same way. Never been indoors, know and protect their turf with their lives. Unless you're in a white vehicle (cops, meatwagon, telephone, gas, power, municipailty) you aren't getting out until you call the phone number posted.