I'll do my best to explain this one but I got a video just in case.

While doing a bounty in Battery Park, one of the areas possible is the construction site in the middle of the zone. Sometimes the AI can run away from you and use a rope that's not supposed to be activated yet. The rope can't be shot down or lowered by the player; it is automatically available after killing a certain amount of enemies. But the rope can be "used" by the AI even when it's not active yet.

You can see the AI doing it at around 50 seconds in the video. When I reach where the rope should be at a 1:17, you can see it is "inactive". I have to run all the way around the zone but the AI can use this inactive rope again (around 3:55). Had walk around back and forth a few times to circumvent this issue as new enemies spawned downstairs and some could use the invisible rope to get to me but I could not use it.

https://www.youtube.com/watch?v=VrSF2Mk_Bsw