Enemies not raiding/Goblins tricked by ladder

Summary:
Enemies aren’t raiding my town for some reason. Recently, I angered a goblin camp and they started sending goblin waves my way, except the 2 goblin waves they sent simply decided to walk through and climb up the ladder, walking into the distance on the mountain until they despawn.

Other enemies that have spawned on top of the mountain have had trouble getting to my town despite the ladder being there, and simply don’t move towards it.

I have moved the ladder from a previous position outside the little wall I built out of slabs, because a similar problem was happening there in which the creatures on the mountain weren’t pathfinding towards it. I know the ladder works, because my townspeople have used it and the goblins have used it.

I have mined inside the mountain and placed my town banner inside there, I’m not sure if this has anything to do with the bug.

Steps to reproduce:

  1. Place ladder
  2. ???
  3. Bug!

I’m not actually sure how to reproduce this bug, I have placed the ladder in 2 different locations and similar problems have occurred.

Expected Results:
Goblin raiding party.

Actual Results:
No party.

Notes:

Attachments:

Version Number and Mods in use:
release-687 Alpha 19