Glow/Spotlight shader reacting different cross-platform

Hi,

I'm working on a project where we use a shader that creates a spotlight/cameralight effect. This effect doesn't seem to work on OSX/Android/iOS and I can't seem to find the reason for that, but it's probably something with OpenGL. The rest of the shader works fine but the spotlight/glow effect reacts way different on Mac.

Could someone please help me on this issue. Pictures and code are posted below.

 Shader "Custom/GlowLine" {
  Properties {
      _TintColor ("Tint Color", Color) = (0.5,0.5,0.5,0.5)
      _MainTex ("Particle Texture", 2D) = "white" {}
      _BrightnessFactor ("Brightness Factor", Float ) = 1.0
      _BrightnessHardness( "Brightness Hardness", Float ) = 2.0
      _LineHardness( "Line Hardness", Float ) = 2.0
  }
  
  Category {
      Tags { "Queue"="Overlay" "IgnoreProjector"="True" "RenderType"="Transparent" }
      Blend SrcAlpha One
      ZTest Always
      AlphaTest Greater .01
      ColorMask RGB
      Cull Back Lighting Off ZWrite On Fog { Color (0,0,0,0) }
      BindChannels {
          Bind "Color", color
          Bind "Vertex", vertex
          Bind "TexCoord", texcoord
      }
      
      // ---- Fragment program cards
      SubShader {
          Pass {
          
              CGPROGRAM
              #pragma exclude_renderers xbox360
              #pragma vertex vert
              #pragma fragment frag
              #pragma fragmentoption ARB_precision_hint_fastest
              #pragma multi_compile_particles
  
              #include "UnityCG.cginc"
  
              sampler2D _MainTex;
              fixed4 _TintColor;
              float _BrightnessFactor;
              float _BrightnessHardness;
              float _LineHardness;
              
              struct appdata_t {
                  float4 vertex : POSITION;
                  fixed4 color : COLOR;
                  float2 texcoord : TEXCOORD0;
              };
  
              struct v2f {
                  float4 vertex : POSITION;
                  fixed4 color : COLOR;
                  float2 texcoord : TEXCOORD0;
                  float4 position : TEXCOORD1;
              };
              
              float4 _MainTex_ST;
  
              v2f vert( appdata_t v )
              {
                  v2f o;
                  o.vertex = mul( UNITY_MATRIX_MVP, v.vertex );
                  o.color = v.color;
                  o.texcoord = TRANSFORM_TEX( v.texcoord,_MainTex );
                  o.position = o.vertex;
                  return o;
              }
  
              sampler2D _CameraDepthTexture;
              
              fixed4 frag( v2f IN ) : COLOR
              {
                  half4 texColor = pow(tex2D( _MainTex, IN.texcoord ), _LineHardness );
                  float brightness = 1.0f / pow(dot( IN.position, IN.position ), _BrightnessHardness) * texColor.a;
                  return 2.0f * (IN.color )* _TintColor * texColor + (brightness * _BrightnessFactor) * 0.1f;
              }
              ENDCG 
          }
      }     
      
      // ---- Dual texture cards
      SubShader {
          Pass {
              SetTexture [_MainTex] {
                  constantColor [_TintColor]
                  combine constant * primary
              }
              SetTexture [_MainTex] {
                  combine texture * previous DOUBLE
              }
          }
      }
      
      // ---- Single texture cards (does not do color tint)
      SubShader {
          Pass {
              SetTexture [_MainTex] {
                  combine texture * primary
              }
          }
      }
  }
  }