Weird lighting with cel shader

I have started to make a basic Cel shader as one of my first materials, so I am new to writing shaders. My problem is that when ever I move thy camera thy lighting seem to change its direction, flipping, I can't figure out thy relation between thy lighting and thy movement of thy camera which would cause it to change. I have looked all over thy web for a solution or a explanation to my problem.
Here is a GIF showing my problem with thy lighting Also here is my code:

 Shader "Unlit/Cel" {
     Properties {
         _MainTex ("Texture", 2D) = "white" {}
         _Color ("Color", Color) = (1,1,1,1) 
         _Threshold ("Cell lighting threshold", Range(1.0, 20.0)) = 5.0
         _Anbient ("Anbient Brightness", Range(0.05, 0.5)) = 0.2
     }
     SubShader {
         Pass {
             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag
             
             #include "UnityCG.cginc"
             #include "Lighting.cginc"
 
             struct appdata {
                 float4 vertex : POSITION;
                 float2 uv : TEXCOORD0;
                 float3 normal : NORMAL;
             };
 
             struct v2f {
                 float2 uv : TEXCOORD0;
                 float4 vertex : SV_POSITION;
                 float3 normal : NORMAL;
             };
 
             float _Threshold;
             float _Anbient;
             float4 _Color;
             sampler2D _MainTex;
             float4 _MainTex_ST;
             
             v2f vert (appdata v) {
                 v2f o;
                 o.vertex = UnityObjectToClipPos(v.vertex);
                 o.normal = mul(float4(v.normal, 0.0), unity_ObjectToWorld).xyz;
                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                 return o;
             }
             
             fixed4 frag (v2f i) : SV_Target {
                 fixed4 col = tex2D(_MainTex, i.uv);
                 float3 normalDirection = normalize(i.normal);
                 float3 lightDirection = normalize(_WorldSpaceLightPos0.xyz);
                 float3 diffuse = _LightColor0 * max(0.0, dot(normalDirection, -lightDirection));
                 half4 cel = half4(floor(diffuse*_Threshold) / (_Threshold - 0.5), 1);
                 return  col * saturate(cel + _Anbient) * _Color;
 
             }
             ENDCG
         }
     }
 }

Also I am using Unity 2017.3.0f1 Personal 64bit. If any one can figure what my problem is and point me in thy right direction or even help me fix I would be very much appreciative of your help, thanks.