Is exactly what i’m saying, i’m sorry for not be specific, you need to expand this menu to see all the options. And remember that every time you change some setting in world settings, you need to recompile the light of your scene
(Don’t just copy it, world settings is relative with your scene)
to be honestly, have a lot of things that need to be improved to have nice seamless shadows and lights with modular structures, with a nice lightmaps, without bleedings, but the most thing that happens, is that you light build scale doesn’t matches with your object scale, and don’t had space enough to build a good lighting and shadows. So, what the scale of your boxes in unreal units? You can meassure it using the grid in top or ortographic views, if you have too small boxes, you need to decrease the lighting scale and rebuild lights (i guess that is your problem), so first try to decrease to 0.3 or 0.5 and rebuild lights to see the results (this can make the lighting built needs more time to compile) if this doens’t work, try to increase the box lightmap resolution in your mesh settings to 128px or more and rebuild to see if this made some diference, you can see the resolution of you lightmap in the scene by pressing Alt+0 and return to lit shading using Alt+4. So let me know if this make your scene looks better. When i work with small modular pieces and i need to have lightmap without this “cuts”, i increase lightmap resolution, or just reduce lightmap building scale in world settings usually one of this works. Let me know if this works.