The first time it happened I thought it was weird. I went to do the Wakako mission where you go and enter a ripperdock's backroom and find out he's harvesting corpos for parts. Don't remember the name. I enter and all enemies inside are dead. I can loot them, they are just... dead. I'm doing the Delamain quest now, Don't Lose Your Mind, and most of the drones are already dead. I didn't kill them. They're just on the floor. I killed 3 drones and the rest are just dead. I don't know when they died or how that happened.
EDIT: Reloading seems to fix it.
EDIT: Reloading seems to fix it.