Video projector artifact

Hello, I'm trying to emulate a video projector and managed to play video using Unity's original projection shader. now, I get the following artifacts:

All solutions I've found are using masks with setTexture command and I'm not sure how to combine it with unity's projection shader that is using 'Vertex & Fragment program'.

This shader

 Shader "Projector/Multiply" 
 {
      Properties 
      {
      _ShadowTex ("Cookie", 2D) = "gray" {}
     _FalloffTex ("FallOff", 2D) = "white" {}
     }
 
 Subshader 
     {
         Tags {"RenderType" = "Transparent" "Queue"="Transparent"}
         Blend SrcAlpha OneMinusSrcAlpha
         ColorMask RGB
         Pass { 
             ZWrite Off
             ColorMask RGB
             Blend DstColor Zero
             Offset -1, -1
             CGPROGRAM
             #pragma vertex vert 
             #pragma fragment frag
             #pragma multi_compile_fog
             #include "UnityCG.cginc" 
 
             struct v2f
             {
                 float4 uvShadow : TEXCOORD0; 
                 float4 uvFalloff : TEXCOORD1;
                 UNITY_FOG_COORDS(2)
                 float4 pos : SV_POSITION;
             };
 
             float4x4 _Projector;
             float4x4 _ProjectorClip;
 
             v2f vert (float4 vertex : POSITION)
             {
                 v2f o; 
                 o.pos = mul (UNITY_MATRIX_MVP, vertex);
                 o.uvShadow = mul (_Projector, vertex);
                 o.uvFalloff = mul (_ProjectorClip, vertex);
                 UNITY_TRANSFER_FOG(o,o.pos);
                 return o; 
             }
             sampler2D _ShadowTex; 
             sampler2D _FalloffTex;
 
             fixed4 frag (v2f i) : SV_Target
             {
                  
                 fixed4 texS = tex2Dproj (_ShadowTex, UNITY_PROJ_COORD(i.uvShadow));
                 texS.a = 1.0-texS.a;
                 fixed4 texF = tex2Dproj (_FalloffTex, UNITY_PROJ_COORD(i.uvFalloff));
                 fixed4 res = lerp(fixed4(1,1,1,0), texS, texF.a);
                 UNITY_APPLY_FOG_COLOR(i.fogCoord, res, fixed4(1,1,1,1));
                 return res * 2;
             }
             ENDCG 
         }
          
     }
 }

Combined with this:

 Shader "MaskedTexture"
 {
    Properties
    {
       _MainTex ("Base (RGB)", 2D) = "white" {}
       _Mask ("Culling Mask", 2D) = "white" {}
       _Cutoff ("Alpha cutoff", Range (0,1)) = 0.1
    }
    SubShader
    {
       Tags {"Queue"="Transparent"}
       Lighting Off
       ZWrite Off
       Blend SrcAlpha OneMinusSrcAlpha
       AlphaTest GEqual [_Cutoff]
       Pass
       {
          SetTexture [_Mask] {combine texture}
          SetTexture [_MainTex] {combine texture, previous}
       }
    }
 }

Thanks!!!