If you're curious how this happened, it's because Automoton patrols are bugged. The way they're supposed to work is the way that the Terminid patrols work, where they spawn in random locations and travel in a random direction across the map until they despawn.
But the bots are broken, and instead their patrols always go to the center of the map, instead of all the way across. When they get there, they just stop, and lock down at that spot. If you've been in the mission for a while and have been doing things that spawn a lot of patrols, you can find a ton of them. Here's a group I caught on Maia last night.
