instantiate objects from right and left of screen to center

Im trying to have objects from either side of the screen one at a time and meet in the middle of the screen on top of each other so a player can jump on them one at a time! i have so far made a empty game object twice and put either side of the screen to instantiate the objects and i have also attached 2 different scripts to them! when the first object is spawn it goes to the center and the second object from the left is delayed with a coroutine and then goes to the center! i want to be able to keep this processing going higher but unsure how without creating many game objects to keep spawning! ive alos noticed some strange behavior! when i play in editor with screen maximised the object on the right does not work but does on small view!

 public class CrateSpawner : MonoBehaviour {
 
     public GameObject crate;
     Vector3 movePosition = new Vector3(0f, .5f, 0f);
     public float speed = 5f;
 
     void Start()
     {
         SpawnCrate ();
     }
 
     void Update()
     {
         if(crate.transform.position != movePosition)
         {
             Vector3 newPos = Vector3.MoveTowards(crate.transform.position, movePosition, speed * Time.deltaTime);
             crate.transform.position = newPos;
         }
     }
 
     public void SpawnCrate()
     {
         crate = Instantiate(crate, transform.position, transform.rotation)as GameObject;
     }
 }
 

script to spawn object from the left side of screen..

 public class CrateLeftSpawner : MonoBehaviour {
 
     public GameObject crate;
     Vector3 movePosition = new Vector3(0f, 1.5f, 0f);
     public float speed = 5f;
 
     void Start()
     {
         //SpawnCrate ();
         StartCoroutine("SpawnDelay");
     }
 void Update()
     {
         if(crate.transform.position != movePosition)
         {
             Vector3 newPos = Vector3.MoveTowards(crate.transform.position, movePosition, speed * Time.deltaTime);
             crate.transform.position = newPos;
         }
     }
         
 
     IEnumerator SpawnDelay()
     {
         
         yield return new WaitForSeconds(2);
         crate = Instantiate(crate, transform.position, transform.rotation)as GameObject;
     }
 }