Anyone have prisoners escape when a caravan returns to the map?

[Kilvas]

Not update specific, but if my caravan returns to map on the northern part of the map, the prisoners instantly have the notification they are trying to escape and do unless arrested in time (Rare for a warden to be near by for return to bed). It's under a mountain next to an auto door and close to the prison. If the caravan spawns anywhere else, it is in open air and the prisoners seem to stay until a warden attends to them, even though it's a few hundred tile walk.

Am I missing something? It seemed to happen around about the time the update that animals needed to be lead to pens, but I also dug through the northern mountain at that time.