OnCollisionEnter/Stay not working when jumping on Enemy

Hi all!

I'd like to know if anyone knows why my collisions (on enemy) stops detecting my player when i jump on it (and stay there)

So the case is:

Player:

2d-SpriteRenderer

CharacterController

2 Scripts - 1 controls movement, another lifebars

Enemy:

2d-SpriteRenderer

Rigidbody

Sphere collider (As collider, physics purpose)

Sphere collider (As trigger, enemy "Aggro" zone)

---

So, when i move Player and enter "aggro" zone, enemy comes to me. When both collide (It's working) my healthbar get's down, but...

If i jump on the enemy, the player just stand here, on the enemy (so there are some sort of collision) but OnCollisionEnter && OnCollisionStay just don't work.

¿Anyone solved something like this?

I'll attach some screenshots ...

OnCollisionEnter/Stay working - My health goes down.

When i stay ON the enemy, OnCollisionEnter/Stay stops working - My health isn't moving anymore..

The code in the Enemy script for collision...

 void OnCollisionStay(UnityEngine.Collision other){
         if (other.gameObject.tag == "Player") {
             GameObject player = GameObject.FindGameObjectWithTag ("healthBar");
             barraVida playerScript = player.GetComponent<barraVida> ();
             playerScript.health -= 3;
             Debug.Log ("STAY"+playerScript.health);
         }
     }

Thanks all !!! :)