Rotation around Z axis wont lock correctly (2D)

I've recently started work on a small space game and im having trouble getting the camera to stop rotation around the Z axis, by this i mean that although the camera does lock it still moves a few degrees out of place, the images below explain it better than i do (i hope)

this image shows what i want the game to look like when the player (spaceship) is rotating, you can see that the edge of the map is perfectly straight

however in its current state when i rotate the player around the Z axis it seem to lock it in the rotation seen in the image below, it wont move any further than this but it still causes the camera to move by a few degrees. I'm very new to unity so i have no real idea why this is happening or how i can fix it, any help would be appreciated and thanks in advance

i only have two scripts in place at the moment, this issue started when i added the locking script (second one)

this script is attached to the player object

 public float forwardSpeed = 10f;
 public float reverseSpeed = 5f;
 public float turnSpeed = 50f;

 // Use this for initialization
 void Start () {
 
 }
 
 // Update is called once per frame
 void Update () {

     if(Input.GetKey(KeyCode.W))
         transform.Translate(Vector2.up * forwardSpeed * Time.deltaTime);
     
     if(Input.GetKey(KeyCode.S))
         transform.Translate(-Vector2.up * reverseSpeed * Time.deltaTime);
     
     if(Input.GetKey(KeyCode.A))
         transform.Rotate(Vector3.forward, turnSpeed * Time.deltaTime);
     
     if(Input.GetKey(KeyCode.D))
         transform.Rotate(-Vector3.forward, turnSpeed * Time.deltaTime);    


     Vector3 mouseWorldPosition = Camera.main.ScreenToWorldPoint(Input.mousePosition);

     Debug.Log (mouseWorldPosition);
 
     }

this script is attached to the main camera, which is a child of the player

 public bool PositionX = false;
 public bool PositionY = false;
 public bool PositionZ = false;

 public bool RotationX = false;
 public bool RotationY = false;
 public bool RotationZ = false;

 private Vector3 temp;

 // Use this for initialization
 void Start () {
 
 }
 
 // Update is called once per frame
 void Update () {

     if (PositionX == true) {
         temp.x = 0.0f;
         transform.position = temp;

     }

     if (PositionY == true) {
         temp.y = 0.0f;
         transform.position = temp;
         
     }

     if (PositionZ == true) {
         temp.z = 0.0f;
         transform.position = temp;
         
     }

     if (RotationX == true) {
         transform.rotation = Quaternion.Euler(0.0f, transform.rotation.y, transform.rotation.z);
         
     }
     
     if (RotationY == true) {
         transform.rotation = Quaternion.Euler(transform.rotation.x, 0.0f, transform.rotation.z);
         
     }
     
     if (RotationZ == true) {
         transform.rotation = Quaternion.Euler(transform.rotation.x, transform.rotation.y, 0.0f);
         
     }    
 }