My image does not get transparent all the way!

Hello!

Mm having some trouble to get my image transparent all the way, when my character goes on a trigger collider a image should pop up and the disappear when exiting the trigger but when exiting the trigger the image has an alpha of 4, but sometimes it does go down to 0 but i dont know why it somtimes does not go down all the way to 0.

Here is my code for the trigger. (fading code is in the end )

 using System.Collections;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class jump_triggers : MonoBehaviour
 
 
 {
   
     public bool onTrigger;
     public Image img;
     public Canvas Canvas_use;
     public Transform player;
    static int y; // trigger once
 
     
     private void Awake()
     {
       
         Canvas_use.enabled = false;
 
     }
 
     // when entring the collider show the canvas
     void OnTriggerEnter(Collider coll)
     {
         if (coll.gameObject.tag == "Player" && y == 0)
         {
             onTrigger = true;
             Canvas_use.enabled = true;
             Debug.Log("test");
             StartCoroutine(FadeImage(false));
         }
         else
         {
             Canvas_use.enabled = false;
         }
     }
 
     //when exiting the collider change to default
     void OnTriggerExit(Collider coll)
     {
 
         if (coll.gameObject.tag == "Player" && y == 0)
         {
             onTrigger = false;
             Canvas_use.enabled = true;
             StartCoroutine(FadeImage(true));
         }
         else
         {
 
             Canvas_use.enabled = false;
         }
         y++; // trigger once
     }
     IEnumerator FadeImage(bool fadeAway)
     {
         // fade from opaque to transparent
         if (fadeAway)
         {
             // loop over 1 second backwards
             for (float i = 3; i >= 0; i -= Time.deltaTime) // fade speed (i)
             {
                 // set color with i as alpha
                 img.color = new Color(1, 1, 1, i);
                 yield return null;
             }
         }
         // fade from transparent to opaque
         else
         {
             // loop over 1 second
             for (float i = 0; i <= 1; i += Time.deltaTime)
             {
                 // set color with i as alpha
                 img.color = new Color(1, 1, 1, i);
                 yield return null;
             }
         }
     }
 }