Weird interaction between addForce and Light

Hi.
I recently started to use light materials and here's the issue I run into during tests:

In this scene, there's a trigger within the cave with a on trigger stay function that sets every object default material to a material with Sprites/Diffuse shader setting, that I called ''Luz2D''.

As you can see, it's working fine with every sprite. Even the boar... but when he starts to run, he turns pitch black and I have no clue why.

I checked every line of the boar's script to find what was causing the error, and turns out that when I remove this piece of code, the error no longer happens:

Code (CSharp):

1.  if (!movingLeft)
2.                 {
3.                     //rb2d.AddForce(transform.right * -moveSpeed);
4.  
5.                     if (rb2d.velocity.x < maxSpeed) // && maxSpeedRestriction) //Enquanto sua velocidade for menor que a max speed, add force.
6.                     {
7.                         rb2d.AddForce(transform.right * moveSpeed);
8.                     }
9.  
10.                     rb2d.transform.localScale = new Vector2(1, rb2d.transform.localScale.y);
11.                 }
12.                 if (movingLeft)
13.                 {
14.                     if (rb2d.velocity.x > -maxSpeed) // && maxSpeedRestriction)
15.  
16.                     {
17.                         rb2d.AddForce(transform.right * -moveSpeed);
18.                     }
19.  
20.                     rb2d.transform.localScale = new Vector2(-1, rb2d.transform.localScale.y);
21.  
22.                 }

I'm absolutely lost. Is there any way to fix this, while keeping the boar's script intact? Why did this happen?
I appreciate your help. Thanks!

EDIT: Digging in deeper, I found out these lines of codes are the problem:
rb2d.transform.localScale = new Vector2(1, rb2d.transform.localScale.y);
rb2d.transform.localScale = new Vector2(-1, rb2d.transform.localScale.y);

 

that worked, thanks!