InvokeRepeating repeating too often with OnTriggerEnter

hey all,

Two unit objects (shooting butterflies in this case) both have sphere colliders with isTrigger checked. Let's call them BF A and BF B.

When BF B collides with the sphere trigger for BF A, BF A runs some code to instantiate a homing missile aimed at BF B and send it towards it.

I am using Invoke Repeating to allow BF A to repeatedly instantiate projectiles at BF B until B is destroyed or exits the trigger sphere.

I am using the time and repeatRate variables in InvokeRepeating to try to control the fire rate. Instead, the unit firing fires off many, many projectiles in rapid succession. I am assuming that InvokeRepeating is getting restarted due to the trigger collision but am not sure quite how that's happening. I am managing the collisions with layers so I don't think there is unwanted collision happening but that might be an issue. Finally, here is the code for the shooter:

 public var projectile:Transform;
 public var projectileSpeed:float = 0.0;
 public var delay:float = 0.0;
 public var fireRate:float = 1.0;
 public var myLayer: int; 
 public var myColorTag: String; 
 public var alreadyFiring: boolean;
 
 //private var projectileCount:int = 0;
  
 // Current player variable
 private var target:GameObject = null;
  
 function OnTriggerEnter(other:Collider)
 {
     if(other.gameObject.tag != myColorTag && other.gameObject.tag != "environment" && other.gameObject.tag != "explosion" && other.gameObject.tag != "Resource" && other.gameObject.tag != "projectile")
     {  
         if (alreadyFiring == true)
 
         { CancelInvoke("Shoot"); alreadyFiring = false; } 
         
         if (alreadyFiring == false) {
 
         InvokeRepeating("Shoot", delay, fireRate);
 
         }
     
         // Store current player
         // NB this assume that you have only one player because it will overwrite second player
         target = other.gameObject;
         InvokeRepeating("Shoot", delay, fireRate); 
         
     }
 }
  
 function OnTriggerExit(other:Collider)
 {
     if(other.gameObject.tag != myColorTag && other.gameObject.tag != "environment" && other.gameObject.tag != "explosion" && other.gameObject.tag != "Resource" && other.gameObject.tag != "projectile")
   //   print ("tested true for tag to shoot. mycolortag: " + myColorTag);
     
     {
         // Remove reference
         target = null;
         CancelInvoke("Shoot");
     }
 }
  
 function Shoot()
 { 
     alreadyFiring = true;
     var shootClone = Instantiate(projectile, transform.position, transform.rotation);
     // Set projectile velocity
     shootClone.gameObject.layer = myLayer; 
     
     var setLayerScript = shootClone.GetComponent(spawnDamageExplosion);
     if(setLayerScript) setLayerScript.myLayerForExplosion = myLayer;
 //    print ("spawned missile and initialized explosion layer to" + myLayer);
     
    
     shootClone.rigidbody.velocity = (target.transform.position - transform.position).normalized * projectileSpeed;
 }