Here is the translucent shadow of some dirty glass rendering correctly in the editor / simulate
And sorry for the very obvious visual aids but here is the problem. When viewing the world from a camera from any character when playing in the editor or in a standalone game, there are no translucency shadows.
The problem persists over many different translucent materials.
Could the answer be some permutation of:
r.TranslucencyLightingVolumeDim
r.TranslucencyLightingVolumeInnerDistance
r.TranslucencyLightingVolumeOuterDistance
???