I’ve been able to recreate this from scratch in a fresh 5.4 project. Our current game went from 5.2-5.4 and exhibits the same behavior. I think I’m just going to wind up fudging reflections in the material with a cubemap, which is super gross but I don’t see any other ways around this. (I’ve heard from a coworker that reflection captures have been incompatible with realtime lighting since UE4 and shouldn’t be used…? Hmm.)