Directional lighting quality

Can anyone tell me why this happens to my lighting when the angle of the directional light is approaching being parallel to a surface?

I seem to be able to lessen the effect by increasing the Shadow Filter Sharpening parameter, however this removes the soft shadow edges, among other issues.

Seeking a deeper understanding of what is happening here as I am relatively new to lighting in UE4

Okay, fairly sure this was a light build issue; building lighting has removed the artifacts.

The source of my confusion was the lack of “Lighting needs to be rebuilt” message because static lighting had somehow become disabled in the project settings