Sorry if this question is already answered in previous threads, but i not find any solution yet searching.
The wooden floor is BSP converted into Static Mesh
With no builded lighting looks fine:
With builded lighting:
Static Mesh config:
Do you get any error about lightmaps overlapping on meshes?
Also, in your UV’s the objects are too close together, you need more space between them, and you need to increase the lightmap resolution.