Moving platform tearing

Hello,

I have created a moving platform. It is made from parts, so it is not a single object. I have applied them to an empty game object, so it is their parent. I am moving the parent object, but the platform is not moving smootly.

Is it because I am not moving the directly, but moving their parent object? If it is the problem, is there any way to fix it?

Update: Here is the code I have wrote to test the up and down movement.

 var ok : boolean = false;
 var ok2 : boolean = false;
 
 function Start () 
 {
     Test();
 }
 
 function FixedUpdate()
 {
     if (ok)
     {
         transform.Translate(Vector3.up * 2 * Time.deltaTime);
     }
 
     if (ok2)
     {
         transform.Translate(Vector3.down * 3 * Time.deltaTime);
     }
 }
 
 function Test()
 {
     yield WaitForSeconds(5);
     ok = true;
     yield WaitForSeconds(5);
     ok = false;
     yield WaitForSeconds(1);
     ok2 = true;
     yield WaitForSeconds(5);
     ok2 = false;
 }