2D and distortion shader

So im trying to make some sort of distortion. Everything looks fine with perspective camera,but doesnt work with 2D/ortographic camera.

Perspective camera

2D/Ortographic camera

Here`s my shader.

 Shader "Effects/Distortion/CullBack+1" {
 Properties {
         _Color ("Main Color", Color) = (1,1,1,1)
         _MainTex ("Base (RGB) Gloss (A)", 2D) = "black" {}
         _BumpMap ("Normalmap", 2D) = "bump" {}
         _ColorStrength ("Color Strength", Float) = 1
         _BumpAmt ("Distortion [0-100]", range (0, 100)) = 10
         
 }
 
 SubShader {
         Tags { "Queue"="Transparent+1" "RenderType"="Transperent" }
         GrabPass {}    
         LOD 200
         ZWrite On
         Cull Back
 
 CGPROGRAM
 
 #pragma surface surf Lambert alpha vertex:vert
 
 sampler2D _MainTex;
 sampler2D _BumpMap;
 
 float _BumpAmt;
 float _ColorStrength;
 sampler2D _GrabTexture;
 float4 _GrabTexture_TexelSize;
 
 float4 _Color;
 
 struct Input {
         float2 uv_MainTex;
         float2 uv_BumpMap;
         float4 proj : TEXCOORD0;
 };
 
 void vert (inout appdata_full v, out Input o) {
     UNITY_INITIALIZE_OUTPUT(Input,o);
     float4 oPos = mul(UNITY_MATRIX_MVP, v.vertex);
     #if UNITY_UV_STARTS_AT_TOP
         float scale = -1.0;
     #else
         float scale = 1.0;
     #endif
     o.proj.xy = (float2(oPos.x, oPos.y*scale) + oPos.w) * 0.5;
     o.proj.zw = oPos.zw;
     
 }
  
 void surf (Input IN, inout SurfaceOutput o) {
         o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap));
        
         half2 offset = o.Normal.rg * _BumpAmt * _GrabTexture_TexelSize.xy;
         IN.proj.xy = offset * IN.proj.z + IN.proj.xy;
         half4 col = tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(IN.proj));
 
         fixed4 tex = tex2D(_MainTex, IN.uv_MainTex) * _Color;
         o.Emission = col.xyz + tex*_ColorStrength;
         o.Alpha = _Color.a;
 }
 ENDCG
 }
 
 FallBack "Effects/Distortion/Free/CullBack"
 }