Take a look at this picture:
As you can see from the picture, some walls have this dark texture after bake lightmap. UVMaps are fine, but have no idea why this happens.
This is the UVMap, walls made by Blender:
Any advice will very appreciate it. Here's my lighting settings:
Using Unity 2018.3.12.f1. Note that all objects are static.
Note that duplicate that object and locate somewhere else and bake looks fine. Only those walls have the issue: