That’s quite strange.
Is this an actual bug or a wanted limitation from Unreal? It appears to happen very randomly as I can subdivide a cube 6 times, so it consists of basically infinitely small faces in my 3d modeling program (blender) but UE4 still accepts the lightmap for it. A school-building I have modeled however has around 70% overlapping UV’s even though they are perfectly fine. I guess I’ll have to start taking my assets apart and making the pieces single objects.
Thanks for the quick answer! That picture looks awesome btw. 