“All my lights are movable. Selecting makes visible the character “selection ring” (golden circles) that’s using the lighting channel 1. I can replicate the problem by just adding a mesh in-game and switching the lighting channel 1 on and off.”
I have encountered a similar issue where viewing the scene from above it, or at a steep angle to it results in the lighting going super bright, at a gradual rate rather than instantaneously. I’m wondering if it has something to do with lighting channel 1. Does it need a specific setup before using it? Why would adding a mesh or using channel 1 or not cause the problem or not, respectively. Or is it another one of those ‘defies simple logic’ problems that UE4 is infamous for.
Is the scene using an LPV (light propagation volume)?
The whole scene is dynamic so I don’t need a light propagation volume… I think? I have a few other things that got push forward from my backlog but I will try this configuration on a clean project as soon as possible and submit a bug report if necessary