Collision (onTriggerEnter) stops working without a reason

Hi, im working on my first real Project in Unity. Its a topdown shooter where enemies appear the top and float downwards where i can either shoot them or collide with them to gain points/lose Hp. My Problem is, that the Collision works a few times but then it suddenly stops and no more Collision will happen.

This is for Collision between the Player and the Enemy:

 void OnTriggerEnter(Collider otherObject)
     {
         if (otherObject.tag == "staticEnemy")
         {
             Debug.Log("Hit");
             if ((getHealth() - 10f) > 0f)
             {
                 // Decrease the player's health
                 decreaseHealth(10f);
                 Destroy(otherObject.gameObject);
                 if (getCombo() > getHighestCombo())
                 {
                     setHighestCombo(getCombo());
                 }
                 setCombo(0f);
             }
             else
             {
                 Application.LoadLevel(1);
             }
         }
     }

This is for Collision between the Projectiles and the Enemy:

 void OnTriggerEnter(Collider otherObject)
     {
         if(otherObject.tag == "staticEnemy")
         {
             Destroy(otherObject.gameObject);
             Destroy(gameObject);
             Player.increaseScore(100f + (Player.getCombo() * 10f));
             Player.increaseCombo(1);            
         }
     }

i cant really recreate when its happening excatly, but usually it works fine for a few hits on the Enemy and losing some Hp. And at some random Point the Projectiles start flying through the Enemy the Player wont collide with the Enemy anymore. Ive already tried changing Collision Detection and a bunch of other Stuff but nothing seems to work. Im not sure if its needed, but post the full code aswell. If its not needed just skip it and thx alot already.

Player script:

 using UnityEngine;
 using UnityEngine.UI;
 using System.Collections;
 
 public class Player : MonoBehaviour
 {
     // HUD
     public static Text playerStats;
     public static Text currentWeaponDisplay;
     public static Text rechargeStateRailgun;
 
     // Scorescreen
     public static Text scorescreen;
 
 
     // Player
     // upgradeable Stats
     public float movementSpeed;
 
     // Variables
     enum ShipModel
     {
         StandardWeapon,
         Railgun,
         Rifle
     }
     public Renderer ShipDisplay;
     public Material StandardWeaponDisplay;
     public Material RailgunDisplay;
     public Material RifleDisplay;
     private ShipModel currentShip = ShipModel.StandardWeapon;
     public float rotationSpeed;
     public float rotationAngleSidewards;
     public float rotationAngleUpwards;
     private static float score = 0;
     private static float health = 100;
     private static float combo = 0;
     private static float highestCombo = 0;
     private static float missed = 0;
     private static float tokens;
 
 
     // Weapons
     enum WeaponEquipped
     {
         StandardWeapon,
         Railgun,
         Rifle
     }
     private WeaponEquipped currentWeapon = WeaponEquipped.StandardWeapon;
     // Standard Weapon Variables
     public GameObject StandardWeaponProjectilePrefab;
     // Standard Weapon upgradeable Stats
     public float speedStandardWeapon;
     public float cooldownStandardWeapon;
     private float nextShotStandardWeapon;
 
     // Railgun Variables
     public GameObject RailgunProjectilePrefab;
     // Railgun upgradeable Stats
     public float speedRailgun;
     public float cooldownRailgun;
     private float nextShotRailgun;
 
     // Rifle Variables
     public GameObject RifleProjectilePrefab;
     // Rifle upgradeable Stats
     public float speedRifle;
     public float cooldownRifle;
     private float nextShotRifle;
 
     // Enemy
     private float spawnTimeEnemy = 1f;
     private bool isSpawning;
 
     // Use this for initialization
     void Start()
     {
         getHUD();
         updateHUD();
     }
 
     // Update is called once per frame
     void Update()
     {
         // Player
         PlayerMovement();
 
         // Weapon
         checkEquippedWeapon();
         StandardWeapon();
         Railgun();
         Rifle();
 
         // HUD
         updateHUD();
 
         // Ship
         updateShipDisplay();
 
         // Enemy
         spawnEnemy();
     }
 
     // Player
     public void PlayerMovement()
     {
 
         // Sidewards
         // Movement sidewards
         float amtToMoveHorizontal = Input.GetAxis("Horizontal") * movementSpeed * Time.deltaTime;
         transform.Translate(Vector3.right * amtToMoveHorizontal, Space.World);
 
         // Rotation sidewards
         float amtToRotateSidewards = rotationSpeed * Time.deltaTime;
 
         if (Input.GetAxis("Horizontal") > 0)
         {
             transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.Euler(0, -rotationAngleSidewards, 0), amtToRotateSidewards);
         }
         else if (Input.GetAxis("Horizontal") < 0)
         {
             transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.Euler(0, rotationAngleSidewards, 0), amtToRotateSidewards);
         }
         else
         {
             transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.identity, amtToRotateSidewards);
         }
 
         // Border sidewards
         if (transform.position.x > 8.4f)
         {
             transform.position = new Vector3(8.4f, transform.position.y, transform.position.z);
         }
         if (transform.position.x < -8.4f)
         {
             transform.position = new Vector3(-8.4f, transform.position.y, transform.position.z);
         }
 
 
         // Upwards
         // Movement upwards
         float amtToMoveVertical = Input.GetAxis("Vertical") * movementSpeed * Time.deltaTime;
         transform.Translate(Vector3.up * amtToMoveVertical);
 
         // Rotation upwards
         float amtToRotateUpwards = rotationSpeed * Time.deltaTime;
 
         if (Input.GetAxis("Vertical") > 0)
         {
             transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.Euler(rotationAngleUpwards, 0, 0), amtToRotateUpwards);
         }
         else if (Input.GetAxis("Vertical") < 0)
         {
             transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.Euler(-rotationAngleUpwards, 0, 0), amtToRotateUpwards);
         }
         else
         {
             transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.identity, amtToRotateUpwards);
         }
 
         // Border upwards
         if (transform.position.y > 0f)
         {
             transform.position = new Vector3(transform.position.x, 0f, transform.position.z);
         }
 
         if (transform.position.y < -4.5f)
         {
             transform.position = new Vector3(transform.position.x, -4.5f, transform.position.z);
         }
     }
 
     // Collision
     void OnTriggerEnter(Collider otherObject)
     {
         if (otherObject.tag == "staticEnemy")
         {
             Debug.Log("Hit");
             if ((getHealth() - 10f) > 0f)
             {
                 // Decrease the player's health
                 decreaseHealth(10f);
                 Destroy(otherObject.gameObject);
                 if (getCombo() > getHighestCombo())
                 {
                     setHighestCombo(getCombo());
                 }
                 setCombo(0f);
             }
             else
             {
                 Application.LoadLevel(1);
             }
         }
     }
 
 
     // Weapons
     public void StandardWeapon()
     {
         if (Input.GetButtonDown("Fire1") && Time.time > nextShotStandardWeapon && currentWeapon == WeaponEquipped.StandardWeapon)
         {
             nextShotStandardWeapon = Time.time + cooldownStandardWeapon;
 
             // Set position
             Vector3 position = new Vector3(transform.position.x,
                                            transform.position.y + (0.6f * transform.localScale.y),
                                            transform.position.z);
             // Fire projectile
             Instantiate(StandardWeaponProjectilePrefab, position, Quaternion.identity);
         }
     }
 
     public void Railgun()
     {
         if (Input.GetButtonDown("Fire1") && Time.time > nextShotRailgun && currentWeapon == WeaponEquipped.Railgun)
         {
             nextShotRailgun = Time.time + cooldownRailgun;
 
             // Set position
             Vector3 position = new Vector3(transform.position.x,
                                            transform.position.y + (0.6f * transform.localScale.y),
                                            transform.position.z);
             // Fire projectile
             Instantiate(RailgunProjectilePrefab, position, Quaternion.identity);
         }
     }
 
     public void Rifle()
     {
         if (Input.GetButtonDown("Fire1") && Time.time > nextShotRifle && currentWeapon == WeaponEquipped.Rifle)
         {
             nextShotRifle = Time.time + cooldownRifle;
 
             // Set position
             Vector3 position = new Vector3(transform.position.x,
                                            transform.position.y + (0.6f * transform.localScale.y),
                                            transform.position.z);
             // Fire projectile
             Instantiate(RifleProjectilePrefab, position, Quaternion.identity);
         }
     }
 
     public void checkEquippedWeapon()
     {
         if (Input.GetKeyDown("a"))
         {
             currentWeapon = WeaponEquipped.StandardWeapon;
             currentShip = ShipModel.StandardWeapon;
         }
         else if (Input.GetKeyDown("s"))
         {
             currentWeapon = WeaponEquipped.Railgun;
             currentShip = ShipModel.Railgun;
         }
         else if (Input.GetKeyDown("d"))
         {
             currentWeapon = WeaponEquipped.Rifle;
             currentShip = ShipModel.Rifle;
         }
 
     }
 
     // Ship Display
     public void updateShipDisplay()
     {
         ShipDisplay = GameObject.Find("Player").GetComponent<Renderer>();
         ShipDisplay.enabled = true;
         if (currentShip == ShipModel.StandardWeapon)
         {
             ShipDisplay.sharedMaterial = StandardWeaponDisplay;
         }
         else if (currentShip == ShipModel.Railgun)
         {
             ShipDisplay.sharedMaterial = RailgunDisplay;
         }
         else if (currentShip == ShipModel.Rifle)
         {
             ShipDisplay.sharedMaterial = RifleDisplay;
         }
     }
 
     // HUD
     public void getHUD()
     {
         playerStats = GameObject.Find("PlayerStats").GetComponent<Text>();
         currentWeaponDisplay = GameObject.Find("currentWeapon").GetComponent<Text>();
         rechargeStateRailgun = GameObject.Find("rechargeStateRailgun").GetComponent<Text>();
     }
 
     public void updateHUD()
     {
         // PlayerStats
         playerStats.text = "Score: " + score.ToString()
             + "\nCombo: " + combo.ToString()
             + "\nHealth: " + health.ToString() + "%";
 
         // current Weapon
         if (currentWeapon == WeaponEquipped.StandardWeapon)
         {
             currentWeaponDisplay.text = "Standard Weapon";
         }
         else if (currentWeapon == WeaponEquipped.Railgun)
         {
             currentWeaponDisplay.text = "Railgun";
         }
         else if (currentWeapon == WeaponEquipped.Rifle)
         {
             currentWeaponDisplay.text = "Rifle";
         }
 
         // recharge state Railgun
         if ((nextShotRailgun - Time.time) > 0)
         {
             rechargeStateRailgun.text = "Railgun ready in: " + (nextShotRailgun - Time.time).ToString();
         }
         else
         {
             rechargeStateRailgun.text = "RAILGUN READY";
         }
     }
 
     // Variables
     public static void setCombo(float x)
     {
         combo = x;
     }
 
     public static float getCombo()
     {
         return combo;
     }
 
     public static void increaseCombo(float x)
     {
         combo = combo + x;
     }
 
     public static void setHighestCombo(float x)
     {
         highestCombo = x;
     }
 
     public static float getHighestCombo()
     {
         return highestCombo;
     }
 
     public static void increaseHighestCombo(float x)
     {
         highestCombo = highestCombo + x;
     }
 
     public static void setScore(float x)
     {
         score = x;
     }
 
     public static float getScore()
     {
         return score;
     }
 
     public static void increaseScore(float x)
     {
         score = score + x;
     }
 
     public static float getHealth()
     {
         return health;
     }
 
     public static void decreaseHealth(float x)
     {
         health = health - x;
     }
 
     // Enemy
     public void spawnEnemy()
     {
         if (!isSpawning)
         {
             isSpawning = true;
             StartCoroutine("waitSomeSeconds");
         }
     }
 
     IEnumerator waitSomeSeconds()
     {
         yield return new WaitForSeconds(spawnTimeEnemy);
         staticEnemy.SetPositionAndSpeed();
         isSpawning = false;
     }
 }
 

Enemy: using UnityEngine; using System.Collections;

 public class staticEnemy : MonoBehaviour
 {
     public static GameObject staticEnemyPrefab;
     private static float currentSpeed;
     private static float minSpeed = 2f;
     private static float maxSpeed = 3f;
     private static float x, y, z;
     private static float MinRotateSpeed = 60f;
     private static float MaxRotateSpeed = 120f;
     private static float MinScale = .8f;
     private static float MaxScale = 2f;
     private static float currentRotationSpeed;
     private static float currentScaleX;
     private static float currentScaleY;
     private static float currentScaleZ;
 
     // Use this for initialization
     void Start()
     {
         
     }
     // Update is called once per frame
     void Update()
     {
         Movement();
     }
 
     public static void SetPositionAndSpeed()
     {
         currentRotationSpeed = Random.Range(MinRotateSpeed, MaxRotateSpeed);
         currentScaleX = Random.Range(MinScale, MaxScale);
         currentScaleY = Random.Range(MinScale, MaxScale);
         currentScaleZ = Random.Range(MinScale, MaxScale);
         // Set new speed
         currentSpeed = Random.Range(minSpeed, maxSpeed);
         // Set new position    
         x = Random.Range(-8.4f, 8.4f);
         y = 4.5f;
         z = 0f;
         Vector3 position = new Vector3(x, y, z);
         Instantiate(Resources.Load("staticEnemyPrefab"), position, Quaternion.identity);
     }
 
     public void Movement()
     {
         float rotationSpeed = currentRotationSpeed * Time.deltaTime;
         transform.Rotate(new Vector3(-1, 0, 0) * rotationSpeed);
         // Move enemy
         float amtToMove = currentSpeed * Time.deltaTime;
         transform.Translate(Vector3.down * amtToMove, Space.World);
         if (transform.position.y <= -5.5f)
         {
             Destroy(gameObject);
             if (Player.getCombo() > Player.getHighestCombo())
             {
                 Player.setHighestCombo(Player.getCombo());
             }
             Player.setCombo(0f);
         }
     }
 }

Projectile: using UnityEngine; using System.Collections;

public class StandardWeaponProjectile : MonoBehaviour {

 private float projectileSpeed;

 // Use this for initialization
 void Start()
 {
     projectileSpeed = 10;
 }

 // Update is called once per frame
 void Update()
 {
     // Move projectile
     float amtToMove = projectileSpeed * Time.deltaTime;
     transform.Translate(Vector3.up * amtToMove);

     // Destroy projectile
     if (transform.position.y > 5.2f)
     {
         Destroy(gameObject);
     }
 }

 void OnTriggerEnter(Collider otherObject)
 {
     if(otherObject.tag == "staticEnemy")
     {
         Destroy(otherObject.gameObject);
         Destroy(gameObject);
         Player.increaseScore(100f + (Player.getCombo() * 10f));
         Player.increaseCombo(1);            
     }
 }

}