Object does not check for collision again after first time

I have to create a protoype game for school about economics, but I'm kind a stuck. It is a simple game where soldiers fight against eachother. Each soldier has his own health and damage. Every soldier has a box collider and a rigidbody attached. I'm checking the collision as followed:

 void OnTriggerEnter (Collider other) {
     if (other.gameObject.tag == "EnemyMelee") {     
         anycollision = true;           
         meleeInSight = true;
         enemyMeleeController = other.GetComponent<EnemyMeleeController> ();
 }

In the OnTriggerExit I simply set the two booleans to false. I have a timer that counts down towards zero and when it reaches zero the soldier simply attacks the enemy and the enemyhealth is counting down to 0 with each hit. When it reaches zero the object is first translated to another position outside the gameworld and then destroyed. Im changing the position so the OnTriggerExit detects it.

When the booleans are set to true the player speed is set to 0 to stop movement and start attacking and when it is set to false the player gains his original speed back, however after one or more collisions the player speed stays solid at its original one and the player never stops.

 void OnTriggerExit (Collider other) {
     anycollision = false;
     meleeInSight = false;
     speed = 5;
 }

In the Update method I'm setting the speed to 0.

 void Update() {
     if (anycollision) {
         speed = 0;
     }
 }