https://i.gyazo.com/608477cd3c2c6eecb8a73d9c72a42b03.jpg
That’s the situation I’ve found today opening my project, till tonite was all perfect, now all the shadows are messed up, strange artifacts everywhere… Btw i’ll get to the hottest point, trying to be as clear as possible, my planks, the model was originally created with 4 planks together, one of them had the UV rotated of 180°, not scaled inward, rotated.
https://i.gyazo.com/2ec606b424837b922d4094a9e24e635a.png
No overlapped UVs.
(ah… was rotated to break the possible similarity of the textures during the repetition…)
btw… I said, oook, so i re unwrapped the planks, now with all the UVs in the same direction… and that’s the result:
https://i.gyazo.com/92396db8ee62a5d2cd8c9fb091a4ec6d.png
And i’ve got 4 planks black and 4 correct… XD Oooooook
And I discovered that the black planks was the ones that i rotated after copying the orginal mesh.
So I tried and… WTF…
https://i.gyazo.com/9b65caa39bf67bd95916e32aa1997d37.gif
The material was getting alternatively black and clear when rotated… GG
The only explanation i’ve found it’s about the Normals… but it’s weird, never happened a thing like this, and it’s not the first time Im doing this kind of stuff O_o
PS. rebuild done and the lightmaps are perfect
Sorry for my english 
**EDIT:
Seems that everything has been messed up, seems that rotating UVs it’s a solution… But it’s crazy WTF, never happened before, always worked like this, in which crazy and Rainbow Unicorns populated world normals works only if oriented in ONE and only direction? O_o **