Instantiating Projectiles not working at certain directions??

Hey, I'm new to Unity and C#, and I am creating a simple game for my application. Sorry if some things sound confusing, Im trying my best to explain my problem. I have 2 players moving in a certain direction. I then coded a script attached to a Bullet Emitter (null object) that follows the player and rotates in the direction the players is walking. From this emitter, the player can fire bullets when he presses "2". The emitter then instantiates a bullet prefab and fires it in the direction of the blue axis of the emitter (ergo the direction the player is walking to, because the emitters script). This works fine in every direction, but when I combine directions (like pos. horizontal and neg. vertical), things go crazy. The bullets spawn in most directions, but in some, bullet copies aren't even instantiated. More detailed: firing bullets in following directions works: walking in + / - horizontal , + / - vertical, + horizontal + / + vertical , -horizontal - vertical. +horizontal -vertical doesnt work

Here are the scripts that might be relevant:

Bullet Emitter

 GameObject Temporary_Bullet_Handler;
 Temporary_Bullet_Handler = Instantiate(Bullet, Emitter.transform.position, Emitter.transform.rotation) as GameObject;
 Rigidbody Temporary_RigidBody;
 Temporary_RigidBody = Temporary_Bullet_Handler.GetComponent<Rigidbody>();
 Temporary_RigidBody.AddForce(transform.forward * BulletSpeed);
 Destroy(Temporary_Bullet_Handler, 3.0F);

Bullet Emitter Repositioner

 public GameObject obj;
     public Vector3 offset;
     public int player;
     private Vector3 xOffset = new Vector3 (0, 0, 0);
     private Vector3 zOffset = new Vector3 (0, 0, 0);
 
 
     void Start () {
         offset = obj.transform.position - this.transform.position;
     }
     
     // Update is called once per frame
     void Update () {
 
         float horizontal = Input.GetAxis("Horizontal" + player);
         float vertical = Input.GetAxis("Vertical" + player);
 
         if (horizontal < 0) {
             xOffset = new Vector3(-2.5F, 0, 0);
         }
         else if (horizontal > 0) {
             xOffset = new Vector3(2.5F, 0, 0);
         }
         else if (horizontal == 0) {
             xOffset = new Vector3(0, 0, 0);
         }
 
         if (vertical < 0) {
             zOffset = new Vector3(0, 0, -2.5F);
         }
         else if (vertical > 0) {
             zOffset = new Vector3(0, 0, 2.5F);
         }
         else if (vertical == 0) {
             zOffset = new Vector3(0, 0, 0);
         }
 
         if (horizontal == 0 && vertical == 0) {
             zOffset = new Vector3(0, 0, 2.5F);
         }
 
         this.transform.position = obj.transform.position - offset + xOffset + zOffset;
         this.transform.forward = obj.GetComponent<Rigidbody> ().velocity;
     }

Hope you can help me!