Drag and Drop 3D objects.

What I'm trying to do is first instantiate an object and then move it around the world in X and Z coordinates and on click of the 0 mouse button, leave the object there. The "Instantiate" function is called via a button. Everything seems to work, but when I move the "newObj" in +Z, the sphere starts jumping. Sometime when I click it doesn't respond and I have to do 2-3 clicks to set the position, is something wrong? public class DragDrop : MonoBehaviour { [SerializeField] GameObject sphere; GameObject newObj; Vector3 pos; bool isDrag;

     void Start()
     {
         isDrag = false;
     }
 
     public void Instantiate()
     {
         RaycastHit hit1;
         Ray ray1 = Camera.main.ScreenPointToRay(Input.mousePosition);
 
         if (Physics.Raycast(ray1.origin, ray1.direction, out hit1))
         {
             isDrag = true;
             newObj = Instantiate(sphere, hit1.point, Quaternion.identity);
             pos = hit1.point;
         }
     }
     void FixedUpdate()
     {
         if (isDrag == true)
         {  
             Ray ray2 = Camera.main.ScreenPointToRay(Input.mousePosition);
             RaycastHit hit2;
             if (Physics.Raycast(ray2.origin, ray2.direction, out hit2, Mathf.Infinity))
             {
                 newObj.transform.position = new Vector3(hit2.point.x, 0, hit2.point.z);
 
                 if(Input.GetMouseButtonDown(0))
                 {
                     newObj.transform.position = hit2.point;
                     isDrag = false;
                 }
             }
         }
     }
 }