http://i.imgur.com/WJWTrmj.jpg

They have an AI package that makes them walk towards a marker in the middle of the cell. They follow the navmesh perfectly, until they reach this spot. They just stop here and scrunch up together. After a bit, they start teleporting past this spot and appearing on the marker. First I tried a generated navmesh which had this problem. Then I hand made the navmesh and still had the problem. Then I leveled out the area with this cliff/ramp and still had the problem. Then I added some rocks to further level it out and still had the problem. Testing the navmesh in CK shows nothing wrong. Any ideas?