It could be VLM settings. Lower detail cell size, and higher maximum memory data per sample, specifically…is what’s suggested. It’s supposed to give finer shadowing and lighting detail. Watching a video in the online learning section about it can help in how to get more detail / quality from the VLM (Volumetric Lightmap). It’s interesting to see this problem over and over, and not even experienced developers know what to do about it. I’m not sure either, but I thought it would be mostly resolved by 4.25.1.