Texture scroll stop when color change

Hi everyone, I create a 3D plateform game. I have a cube which have two differents textures: one for the upper face and one for the others faces. This cube have a little script which scroll the upper texture:

 public class ScrollingTexture : MonoBehaviour
 {
     public float scrollSpeedZ = 0.90f;
     public float scrollSpeedX = 0.90f;
     public Material mat;
     private void FixedUpdate()
     {
 
         float offset = Time.time * scrollSpeedZ;
         float offset2 = Time.time * scrollSpeedX;
         mat.mainTextureOffset = new Vector2(offset2, -offset);
     }
 }

This works well but the player can also change the materials color of this cube:

 public void SetColor(Color color)
     {
         foreach ( Material m in GetComponent<Renderer>().materials)
         {
             m.color = color;
         }
     }

And when SetColor is called, the texture scrolling is stopped... Whereas mat.mainTextureOffset is still evolving !

What is going on? Thanks