New to Unreal: How to troubleshoot low resolution shadows on small objects?

Development Rendering
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I am VERY new to unreal but I have used other game engines before. I am making a puzzle game with small 3d objects, the largest of which is 8 inches across. I thought I would do the “right”(?) thing by using real world dimensions to model these pieces in Blender and pull them over to Unreal. Their shapes look perfect, but their shadows:

  1. Have visibly jagged edges.
  2. Have some speckling.
  3. Flicker, sort of like CRT TV static.

Example:
image

My lighting setup:

  • Default sky atmosphere, directional light, and sky light from the empty project template.
  • Pieces are dynamic.
  • Table is static (a scaled up primitive cube).
  • I chose “mobile” project type, maybe relevant?

What I’ve tried:

  1. Setting lighting quality to production.
  2. Selecting the directional light and maxing out the shadow resolution slider.
  3. Scaling everything up 10x.