Instantiating from different Sources causes collision inconsistency

hi all,

My game has a fireball skill which i call a create method on from inside my Entity classes. This works fine, however, when both my player and enemy classes are creating fireballs at the same time, the collision detection becomes faulty; there seem to be runs of non-detection on either the player or enemy collisions with the fireball before it suddenly resumes detection. I find no detection feedback during this time and, strangely, this only happens when both are using the fireball skill at the same time.

I've tried fiddling with the continuous dynamic properties on all prefabs but it doesn't change anything, I've also tried reducing the fixed timestep in Project Settings -> Time, nothing.

below is the create method from within the fireball class, the onTriggerEnter is very simple, I don't think the issue's in there. The only solution I've found so far is to have the enemy and player classes call two identical scripts which are different classes which works 100% but it's not a great solution.

Is there something I'm missing?

 public static Entity owner;    
 public static Fireball Create(int level, GameObject Fireball, Entity caster, Transform entityLocation)
 {
     owner = caster;
     GameObject newFireball = Instantiate(Fireball, entityLocation.TransformPoint(Vector3.forward * .4f + Vector3.up * .5f)
         , entityLocation.rotation) as GameObject;
     Fireball fireball = newFireball.GetComponent<Fireball>();        
     //set parameters
     Rigidbody fireballRB = newFireball.GetComponent<Rigidbody>();
     fireballRB.velocity = entityLocation.TransformDirection(Vector3.forward) * 6;
     return fireball;
 }

thanks in advance,