Graphics.DrawTexture with Shader not working on iOS?

I am trying to quickly finish a demo so that it can be presented however I am currently struggling with the drawing of a very simple shader via Graphics.DrawTexture.

The code works on both Windows & Mac Editor, however once loaded on iOS, the texture simply appear black. I attempted remove the moving effect, the coloring, removing parameters, increasing the texture size but nothing works.

Here's an exemple of a really simple shader that should have worked :

 Shader "Custom/MovingVertexLit" {
     Properties {
         _MainTex ("Base (RGB)", 2D) = "white" {}
         _Color ("Main Color", COLOR) = (1,1,1,1)
     }
 
     SubShader {
         Tags { "RenderType"="Overlay" }
 
 
             CGPROGRAM
             #pragma surface surf Lambert 
 
             sampler2D _MainTex;
             float4 _Color;
             
             
             struct Input {
 
                 float2 uv_MainTex;
 
             };
 
 
             void surf (Input IN, inout SurfaceOutput o) {   
                 half4 c = tex2D (_MainTex, IN.uv_MainTex);
                 fixed4 output = tex2D(_MainTex, IN.uv_MainTex += 0.5 * _Time);
                 o.Albedo = output.rgb  * _Color;
                 o.Alpha = output.a;
             }
             ENDCG
         }
         FallBack "Diffuse"
     }

-OpenGL ES 2.0 is being used.

-Display buffer is already set to 32-bit.

I am really out of idea and I have no clue why a simple shader drawn on a GUI would be such a problem. Anyone has any idea of what is happening? :(