asset wont accept attached script

hi all, i have a Problem with an .obj-asset i try to Import to my Scene at runtime.

i have a script, which adds the asset. part of the script is following (the script works and the asset gets imported!):

 if (itemLabel.Equals("Quelle"))
 
                 {
 
                     GameObject cube = OBJLoader.LoadOBJFile("path.obj");
 
                     cube.transform.position = new Vector3(x, y, z);
 
                     cube.transform.name = items[0];
 
                     cube.transform.tag = "Plant";
 
                     cube.transform.localScale = new Vector3(1, 1, 1);
 
                     cube.AddComponent<DragViaMouse>();

as you can see i want to add a component (another script : DragViaMouse) to my newly added Gameobject (which is the .obj-asset)

the script i want to add is following:

 public class DragViaMouse : MonoBehaviour
 
 {
 
 
 
 
     public Vector3 screenSpace;
 
     public Vector3 offset;
 
     public float speed = 100;
 
 
 
 
     Vector3 dist;
 
     Vector3 startPos;
 
     float posX;
 
     float posZ;
 
 
 
 
     void OnMouseDown()
 
     {
 
       
 
         startPos = transform.position;
 
         dist = Camera.main.WorldToScreenPoint(transform.position);
 
         posX = Input.mousePosition.x - dist.x;
 
         posZ = Input.mousePosition.z - dist.z;
 
     }
 
 
 
 
     void OnMouseDrag()
 
     {
 
         float disX = Input.mousePosition.x - posX;
 
         float disY = 0;
 
         float disZ = Input.mousePosition.y - posZ;
 
         Vector3 lastPos = Camera.main.ScreenToWorldPoint(new Vector3(disX, disY, disZ));
 
         transform.position = new Vector3(lastPos.x, startPos.y, lastPos.z);
 
     }
 
 
 
 
     void OnMouseOver()
 
     {
 
         if (Input.GetAxis("Mouse ScrollWheel") > 0)
 
             transform.Rotate(Vector3.up * speed * Time.deltaTime);
 
 
 
 
         if (Input.GetAxis("Mouse ScrollWheel") < 0)
 
             transform.Rotate(-Vector3.up * speed * Time.deltaTime);
 
       
 
         if (Input.GetKeyDown("[7]"))
 
                 transform.localScale += new Vector3(10f, 0, 0);
 
         if (Input.GetKeyDown("[8]"))
 
             transform.localScale -= new Vector3(10f, 0, 0);
 
       
 
         if (Input.GetKeyDown("[4]"))
 
             transform.localScale += new Vector3(0, 10f, 0);
 
         if (Input.GetKeyDown("[5]"))
 
             transform.localScale -= new Vector3(0, 10f, 0);
 
 
 
 
         if (Input.GetKeyDown("[1]"))
 
             transform.localScale += new Vector3(0, 0, 10f);
 
         if (Input.GetKeyDown("[2]"))
 
             transform.localScale -= new Vector3(0, 0, 10f);
 
 
 
 
     }
 
     private void OnCollisionStay(Collision collision)
 
     {
 
       
 
     }
 
 }
 
 
 
 
 
 
 
 
 
 

the Problem i now have is that the asset wont accept my script. i cant use any commands written in the script(dragviamouse). if i try to add the script to a primitive object like a cube or a sphere everything works fine and is changeable. why is that? what am i missing?