Light leaking in shadows from directional light

I’ve got a scene set up with a stationary directional light for the sun that is basically backlighting a rocky mountain-like piece of geometry (static mesh). In the area that should be completely shadowed there are very bright little bits of light that are leaking through. I have attached a screenshot of what it looks light backlit and what it looks like from the side where you can see the angle of where the light is coming from and how it should be shadowing the geometry.

I’ve tried everything I can think of to fix this. I brought the directional light Shadow Bias and Shadow Slope Bias both to 1 and then to 0, but neither of those had any effect. I played with the Contact Shadow Length, but that screwed up everything. I increased the lightmap resolution all the way to 4k, but that did nothing. I played around with a bunch of the lightmass world settings, but none of those did anything either. I also tried selecting Two Sided Shadows on the object.

What do you think could be causing this? Is it just my hardware maybe? I have an older 980 Ti. Is it possible that the UVs for the lightmap are the problem? I am having Unreal generate that automatically at 1024.

Thanks for taking a look. I am very new to Unreal, coming over from 3ds Max after 20 years, so there’s a lot that has been stumping me when trying to convert scenes.