What could cause an actor to cast only half a shadow?

The trees in the image below are a single actor. I cannot figure out why the shadow is cut off along the obvious diagonal line.

I have tried adjusting the light source, adding and importance volume, and adjusting the shadow settings on both the trees and the ground that they are on. The actors are all movable and the light sources are as well.

Checking the box “Single Sample Shadow from stationary Lights” for the trees causes the shadow to reach farther but still it is cut off.

Any suggestions what might be causing this?

I’m having this issue right now and it’s driving me insane. Were you ever able to figure this out?