Changing Lightmass World Settings causes this

I’m convinced a couple changes I made in my lightmass settings in the world settings caused this strange artifact on the floor of my scene. I have a directional light coming in from the son, being occluded by multiple beams, but then showing a sort of spiral shadow on the floor. Why is this?

Here are my lightmass settings:

Here’s the strange shadow:

And here’s the lightmap density, which clearly shows it’s not the problem:

Is the light set to static? Do you have a lightmass importance volume? What are the lights shadows set to?

The directional light (the sun) is set to static. I do have a lightmass importance volume placed appropriately.

I don’t know what you mean by “What are the lights shadows set to.”