Thanks Tim. No, the offending object is a box. What is happening is the indirect lighting (whether it be from a directional light, point light or spotlight) gets abruptly cut off and lighting does not look continuous. Visually, this looks exactly like the first image in this thread, where the bounce light from the sun is hitting the floor and gets abruptly cut off. The first 2 row of tile on the right seem fine (look orangish due to the bounce) but the ones in the middle are dark.