Can't transform position of an object after a certain point. Help?

I'm trying to make a Space Invaders Remake, and I'm having a hard time programming the AI movement. In t$$anonymous$$s case I'm trying to make the enemies move from the left to the right and so on using t$$anonymous$$s code:

 using UnityEngine;
 using System.Collections;
 
 public class GroupMovement : MonoBehaviour
 {
     float maxUnits = 2;
     float unitsToMove;
     Rigidbody2D rb;
     bool movingR = false;
     bool movingL = false;
 
     void Start()
     {
         rb = GetComponent<Rigidbody2D>();
         InvokeRepeating("moveR", 1, 1);
     }
 
     void moveR()
     {
         movingR = true;
         unitsToMove = unitsToMove + 1;
         transform.position = new Vector2(rb.position.x + 1, rb.position.y);
     }
 
     void moveL()
     {
         movingL = true;
         unitsToMove = unitsToMove + 0.5f;
         transform.position = new Vector2(rb.position.x - 1, rb.position.y);
     }
 
     void Update()
     {
         Cancel();
     }
 
     public void Cancel()
     {
         if (unitsToMove > maxUnits && movingR == true)
         {
             CancelInvoke("moveR");
             unitsToMove = 0;
             InvokeRepeating("moveL", 1, 1);
         }
         if (unitsToMove > maxUnits && movingL == true)
         {
             CancelInvoke("moveL");
             unitsToMove = 0;
             InvokeRepeating("moveR", 1, 1);
         }
     }
 
     void moveDown()
     {
         transform.position = new Vector2(rb.position.x, rb.position.y - 1);
     }
 
 }

It works at the begining but once it starts to move left it gets wierd. I don't know if it is some problem with the code it self or just a dumb mistake, but after a couple of moves it starts to transform the position way more than "1".

Could someone help me with t$$anonymous$$s?