Yes they are, just double checked
As you can see from this screenshot, lighting looks different on differnet clones of the same static mesh, even after compiling lights… what can I do?
I am using default materials and meshes from the UE4 starter pack
Are they all exactly the same height? ( Z coord )
EDIT: Tried it with the same material, same problem. Don’t know the answer actually. I also tweak the material, it’s not that…
EDIT2: It’s to do with the lightmap… gimme a little time…
EDIT3: I tried various lightmass tweaks, but it looks the same. I think it’s like Makigirl says, one big mesh. Or, dynamic directional light and stationary skylight, that works great 
Thank you so much, that fixed it!! Also managed to keep light compiling time under control luckily!
Can you add this as an answer, so it can helps more people that encounter a similar problem?
Unreal calculates light per mesh.
If you don’t need modular pieces: use one mesh for the floor!
If you do need:
in lightmass go with 0.1 for indirect lighting scale + 0.6 smoothness and the lighting differences will disappear!
BUT!
Highly possible that you’ll discover “patchy” result due to low indirect lighting quality which you’ll need to raise…
Both scale and quality will raise the building time by a lot!
Cool! I’m glad it worked out for you!