Loading a Map in the Map Editor causes Visual Bug with Walls

When loading up a previously worked on map, claimed walls do not render properly; the north and eastern sides are invisible. Unclaimed walls are unaffected, and strangely, impenetrable rock renders its natural walls on sides where claimed walls would otherwise appear.

On the minimap, you can see my rotation. In the upper left, you can see the impenetrable rock not rendering correctly on the claimed shrine and treasury. In the lower right, you can see the claimed walls not rendering at all.