Why do shadows still show up with "receive shadows" unchecked?

Very strange, and I'm wondering what's causing this. In the scene:

hangar environment, set to receive shadows (not cast them)

4 directional lights near the ceiling, all set to Soft Shadows, Render Mode = Auto

1 spot light inside the cabin of the helicopter, set to no shadows

4 cameras (1 perspective, 3 orthographic), all set to "player settings" rendering (which is deferred rendering)

helicopter exterior set to receive and cast shadows

helicopter interior set NOT to receive nor cast shadows

I have not baked any lighting. Materials are standard diffuse shaders.

So... why is my cabin interior still receiving shadows even though I have unchecked that option?

Set to NOT receive shadows:

Set TO receive shadows:

You can just barely see in the second image that the shadows are received in the top-right camera view, but the Main Camera doesn't seem to care what the shadow settings are.

Also, I've noticed that of the 4 directional lights, one of them is a darker shade of orange in the Scene view (not sure what this means).

This is purely an aesthetic thing, as far as I can tell. It's just very troubling that my objects aren't doing what I tell them to. I'm wondering if it has something to do with having multiple cameras, too many lights, the interior being a concave mesh, the object having multi-subobject materials (much to my chagrin) or something I'm completely overlooking.

I've tried re-importing all assets, copying the project and re-opening, setting the lights to Spot instead of Directional; none of these seem to have any affect on shadow behavior.

Using Forward Rendering fixes the issue, but then I only get one light casting shadows.

Best thing that's worked so far is to change the material of the interior from Diffuse to Unlit Texture,but why should I have to do that?.

Any insight is appreciated.

Sadly, I don't believe I'll be allowed to upload any project files. Images and written descriptions will have to suffice.