Animations are jerky? with FOV and aspect ratios

so i have a sniper rifle and my aim down sights is a combination 2 scripts, one that changes the main cameras field of view and another that plays an animation to bring the sniper to eye level. both while holding right click

the FOV works and the animation stops before it reaches eye level sometimes it will jerk and get stuck also if i have maxmize on play selected it will always jerk or any other size then 2 by 3

for the animation below

var AnimName ="scopeinsniper";

//private var resetTime = .0000000000000000;

var useBackwards = true;

function Update (){

if(useBackwards==true){

if(Input.GetMouseButtonDown(1)){

animation[AnimName].speed = 2;

//animation[AnimName].time = resetTime;

animation.Play(AnimName);

}

if(Input.GetMouseButtonUp(1)){

animation[AnimName].speed = -2;

//resetTime =animation[AnimName].time;

animation[AnimName].time = animation[AnimName].length;

animation.Play(AnimName);

for FOV

public var FOVIN :float = 35;

   public var FOVSpeed :float = 5;
   
       public var Aim : boolean = false;
       
           public var DeffFOV : float;
           
            public var CAM : GameObject;

function Awake(){

 DeffFOV = CAM.camera.fieldOfView;

}

function Update () {

  if(Input.GetMouseButtonDown(1)){
  
   Aim = true;
   
  

} if(Input.GetMouseButtonUp(1)){

   Aim = false;
   
  
  
 }
 
 
        if(Aim){
        
        CAM.camera.fieldOfView = Mathf.Lerp(CAM.camera.fieldOfView, FOVIN , FOVSpeed * Time.deltaTime);
        
        }
        
        if(!Aim){
        
        CAM.camera.fieldOfView = Mathf.Lerp(CAM.camera.fieldOfView , DeffFOV , FOVSpeed * Time.deltaTime);
        
        }
        

}