CalculatePath often returns wrong results

I have buildings in my navmesh that are marked as "not walkable", but sometimes, when the building is at a particular position, calculating a path towards the inside of the building returns a complete path. As a result, my character walks up to the building the keeps walking into the side of it, because it thinks there is a valid path to the center.

When I move the building to another position, it seems to fix this issue. What could be the underlying cause of this? What parameters in the navmesh generation should be tweaked to fix this?