Prop Materials render incorrectly w/ambient lighting until any prop is selected

Hello all!

I've used Unity for over a decade and never experienced this bug before. I make a procedurally generated world, which works fine, then I populate it with various props. Their materials rendered correctly when I used no ambient lighting, but when I added ambient lighting they began to show this strange hyper-emissive look, as if they had an HDR color turned up to +10.



I tried removing the directional lights from the scene - same problem. (I want to use ambient light only since this is a spherical game map and the only lighting that would make sense is either ambient or light coming from the camera's perspective.) The weird thing is, when I select any prop in the hierarchy, the materials of ALL the props update and render correctly. The props use close to a dozen different materials, all with different shaders ranging from Built-In Opaque to Cutout to Transparent.

Has anyone experienced this bug before? How do I "touch" an object at runtime to force a lighting refresh?

BTW I was using 2021.1.1. Tried upgrading to 2021.1.14 and 2021.1.23 (latest) but no change.

 

Bump. Please help me This is a pretty major obstacle to my project.