Creatures are teleporting into my base, especially when I took so much time and afford make walls and other security features like gates. I have heard in some video that It is intentional, to prevent abuse. I would understand If somebody would build on top of rock, but on the ground where are all places reachable It makes no sense. I would rather to NPCs try to destroy doors/gate or even walls If they can not find door/gate. Plus after my thralls are fighting then they go back on place with totally wrong rotation and placement. So I have to relocate them after every fight.
Is this during a Purge?
If not, what’s the context?
Also, screenshots would help figuring this out 
Nope, It is not purge. I am close to It, but I guess It will be same problem what I read on Reddit from users.
You can simulate It easily, just make base with doors/gates and walls, make open area inside. Go to your base and close door so enemy NPCs will stay outside. After few seconds they will teleport to you.
No, I think they are spawning in your base. Could be wrong, but the reason I have grown to hate purges is they spawn in or on your base.
I have base in H3 behind that pointy rock. I were in my base, chilling then suddenly exiled warrior spawned inside my base. I am far from their camp. Maybe just random spawn, dumno. Another example when in nearest camp elite crocodile spawned. I aggro him, then run into my base and closed gate. After few seconds He ported behind gate to me. Now I tried It again with regular crocodile and He did not ported and lost aggro after some time, which is correct. So maybe It was just some problem with collision.