Can't build lighting on 2017 iMac ("LightmapCoordinateIndex" location?)

I was trying to create a lighting example for a proof-of-concept for project, but found myself in a bit of loop. The issue is that I’m trying to build the lighting, however, when I build the lighting there is an issue and UE4 tells me to check the message log. I check the message log and it tells me that the “Maps need lighting rebuilt.” Okay, rebuild lighting… enter recursion Hell.

Looking at the documentation it tells me that there are 2 “common” possibilities; 1)" lightmap resolution of 0" - if I’m looking in the right place (LODSystem) then it’s 256 and not 0. So far, so good. 2) “LightmapCoordinateIndex out of bounds” - I can’t find this anywhere. I’ve looked under World Settings, Project Settings, and Editor settings. Where is this setting? I’ve done a few searches and just can’t find it.

Things to consider:

  • I started with the Blank Level template
  • I created a new blank level
  • Lighting in the level - Atmospheric Fog, BP_Sky_Sphere, DirectionalLight, and SkyLight
  • I’m using “Build Lighting Only”

Side note - Right before sending this I decided to try and create another project (Same Actors as above) from scratch just to be doubly sure. This time the lighting build just fails, no message log errors or warnings.