Not 100% sure if this is a bug or not, but I wanted to bring it up.
I was raiding the NPC garrison withing 3-4 mins of it spawning. My path was through the back corner and I just a locked crate in a couple of walls. The second I hit the crate the garrison started breaking down. It had been a very short amount of time from the first boom to touching the crate and it felt the garrison started breaking down way too soon. I was unable to investigate any other loot areas because of the rapid breakdown.