A bit of an UPDATE.
If the bForceNoPrecomputedLightning function is applied (World settings: “Force No Precomputed Lightning”), it’s returning the message: “…enabled, build lightning once to propagate the change (will remove existing precomputed lightning data).”. So obviously until this is done manually your level will hold some precomputed lightning data. Wondering if that junk cache files would migrate to the release compiled project if the option is not enabled (think of a mix of some dynamic lightning and some stationary in your level, and figure what possible junk cache the engine is adding to your final compilation and what is not a junk).