Problem with lightmap ( with images )

Hi , First of all sorry for my bad english , i hope you will understand my problem:)

i’m working on a project for IOS and android with some friends.
It’s a runner like ( minion rush , sonic dash , temple run )
And here is my problem:

I have create 9 big pattern bloc that will spawn in front of each other to allow the player to run forever .
So i created for each pattern , a second UV for lightmap.

I imported all of my pattern on unity and started to try to lightmap my game

BUT , only one pattern on 9 is good and without bug.
All the 8 other patterns have THE SAME bug : some part of my pattern are very black .
here is some screenshot to understand better the problem.

Good , no bug here :

Bad, bug :

Solved it by changing the normal and tangeant import option in unity from IMPORT to Calculate