The engine doesnt have a proper Runtime GI.
Normally, you put “stuff” in the doorways that didables or reduces the skylight settings when yku enter.
Also, a properly made Manifold model will prevent bleeding much better than adjacent or even overlapping objects.
Thats generally why in Modular Kits you make Corners that can be used directly as corners.
In ue4.x you can sort of levarage distance fields to somewaht adjust the bleed by way of forcing more shadow - which somewhat also helps get the room darker when you disable or control auto-exposure.
Using Baked Light mentioned above would fail btw.
As I said, you can’t stack random objects and expect the lightmap to work right after bake.
You need precise models with correct light UVs and honestly, to enclose a room for a light build- not only would the model need to be merged (which is just best practice), but you would probably also have to give it a double shell made of 1m thick engine blocks in order to prevent any light from baking in the exterior of the walls;
Thanks to the total mess that the engine makes of shaders, any light hitting the mesh anywhere will results in light bleeding thorugh to the other side of a double sided manifold mesh…
Additionally, the shadowing artifact you see at the junctures is more a result of TAA than the engine’s light of DFAO/light calcs.
Youd get almost no artefacts in forwardshading mode. Which is something to at least consider…