Shadow leak from objects behind wall in single static mesh

I’m currently testing out stuff with Blender and UE4 and I’m getting a very odd lighting issue, instead of the often asked for seam leaks (which I’ve been able to fix after lot’s of searching online) I’m having the issue that the walls behind one big wall are leaking through as shadows. I’m not entirely sure how to describe it and it’s a very odd behavior.

I have already UV-Unwrapped the individual objects (each wall is it’s own object and they’re all 20cm thick, there are no planes in the scene) in blender with the Lightmap Pack option. I’ve also increased the Lightmap Resolution within UE4 which made it look a lot nicer but the error just became more obvious.

Here’s a screenshot of what I’m seeing in UE4

[And here is the .blend file of this prison (it’s just a main hall with a overhang for the security station and 4 cell blocks, nothing more the a bunch of cubes in the right formation) if there may be a problem with the .blend file][2]

Would anyone know what is going on here? Oh and quick note, there is only 1 single light in the entire scene in the UE4 project, that is the point light in the middle of the hall that you can see in the screenshot, I’ve already deleted the skylight since I won’t be needing it when the Prison model is finished (it will be a closed off prison without any outside areas)

I just checked the UV map of the static mesh within UE4 and every single UV map are overlay-ed on each other, is that normal (since each wall/floor/roof is it’s own separate object) or might this be the issue? (would be weird if this was true because all the shadow leaks are exactly where the wall are behind them)

I’m having the same issue as you do.

In UV channel 0, it’s normal for them to overlap.
The one that shouldn’t is the channel 1, as it’s used for the lightmap.