So I made a set of wall pieces with the same smoothing groups so they can be seamlessly placed beside one another but this keeps happening between them:
Clearly there is something going on here because when I flip them around and put them facing the light directly I get this:
So yeah, Im a little confused. What do you think this could be?
Thanks everyone 
-Jordan
Hi Jordan,
The difference you’re seeing here is indirect light from global illumination when building static lighting. When it’s flipped towards the light you’re seeing direct light on the object that would wash out any seams that would be created due to indirect lighting bake.
This thread on the forums will walk through a number of solutions to help resolve this: Modular Asset Lighting Problem - Rendering - Epic Developer Community Forums
The most common ways to resolve this are to try adjusting the World Settings > Lightmasss > Lighting Quality (set to 2) and Lighting Smoothness (~.65).
This will smooth the lighting samples between the two assets,
Making sure that your lightmap UVs snap the correctly spaced grid lines determined by your target lightmap resolution will also help.
Other options include making this a single wall mesh and making it overly modular, or using geometry to cover the seams that are created.
Feel free to ask any questions if you have them.
Tim
