On Trigger Enter no longer works? long delay to activate

i've experienced similar issues with triggers and colliders sometimes to fix these u can change the rigidbodys collision detection to continuous, if this doesn't help you maybe you change some of your system to be a raycast, as for your trigger delay i can't be sure of the cause but if i were to speculate i would have to wonder how much information your script processes before doing something with the trigger i'll provide a couple of my own methods for using triggers to define an object for interaction and also a simple raycast that i use to loot items which should be easy to adapt for alot of cases such as shooting bullets.

 this is my method for assigning an interactable object. u can place this on any object that has a trigger.
 
     void OnTriggerEnter(Collider Other){
         if (Other.gameObject.tag == "Player") {
             PlayerInteraction pit = Other.GetComponent<PlayerInteraction>();
             if(pit.interTarg == null) {
                 pit.interTarg = gameObject;
             }
             if(pit.interTarg != null) {
                 pit.nextTarg = gameObject;
             }
         }
     }
     void OnTriggerExit(Collider Other){
         if (Other.gameObject.tag == "Player") {
             
             PlayerInteraction pit = Other.GetComponent<PlayerInteraction>();
             if(pit.interTarg == gameObject && pit.nextTarg != null) {
                 pit.interTarg = pit.nextTarg;
                 pit.nextTarg = null;
             }
             if(pit.interTarg == gameObject && pit.nextTarg == null) {
                 pit.interTarg = null;
             }
         }
     }
 }
 
 // a brief breakdown of how it works this assumes that the Player has a script called PlayerInteraction upon this PlayerInteraction script there is 2 GameObject Variables one named interTarg, which is the current target for interaction. and nextTarg ,this is for if we manage to stand on 2 triggers simaltanously.
 and note that you will never need to make changes to the above
 since u will be doing everything with these Interactions within your PlayerInteraction a simple example to be used in playerinteraction below.
 
 // first checking if we have a target of interaction.
 if(interTarg != null) {
     // this is where would check information regarding the target
     // before we do something to it
     if(interTarg.tag == "Shop") {
         showShopGUI = true;
 }
 }
 // then i would go on to use that bool for some GUI display.
 
 // Forward Raycast from our cam, hit represent the impact point of the ray
 // i use it below to see if we hit a transform then check the name of that transform
 // before accepting an input key to pick the item up
         RaycastHit hit = new RaycastHit ();
 /// uncomment below to see the raycast in the scene.
         //Debug.DrawRay (GetComponentInChildren<Camera>().transform.position, GetComponentInChildren<Camera>().transform.forward * 3f, Color.blue, 1f);
         Physics.Raycast (GetComponentInChildren<Camera>().transform.position, GetComponentInChildren<Camera>().transform.forward * 3f, out hit, 15f);
         if(hit.transform != null && hit.transform.tag == "Loot") {
 
             if(Input.GetKeyDown(Keycode.E)) {
                 LootItem(hit.transform);
             }
         }

// if i was unclear on anything or u need help understanding something i didn't cover feel free to email me Skylem@live.com.au appologies for the long winded answer, i did my best to only include information relevant to a possible solution