Unity Shader Error when Building to WebGL

Question

When trying to build my game to Webgl I receive the following errors:

Shader error in 'Hidden/Universal/CoreBlit': invalid subscript 'positionCS' at /PathToProject/Library/PackageCache/com.unity.render-pipelines.core@12.1.2/Runtime/Utilities/Blit.hlsl(92) (on gles)

Shader error in 'Hidden/kMotion/CameraMotionVectors': SV_VertexID semantic is not supported on GLES 2.0 at line 11 (on gles)

The Shader I am using has the following code:

Shader "Skybox Gradient"
{
    Properties
    {
        _Top("Top", Color) = (1,1,1,0)
        _Bottom("Bottom", Color) = (0,0,0,0)
        _mult("mult", Float) = 1
        _pwer("pwer", Float) = 1
        [Toggle(_SCREENSPACE_ON)] _Screenspace("Screen space", Float) = 0

    }
    
    SubShader
    {
        
        
        Tags { "RenderType"="Opaque" }
    LOD 100

        CGINCLUDE
        #pragma target 3.0
        ENDCG
        Blend Off
        Cull Back
        ColorMask RGBA
        ZWrite On
        ZTest LEqual
        Offset 0 , 0
        
        
        
        Pass
        {
            Name "Unlit"
            Tags { "LightMode"="ForwardBase" }
            CGPROGRAM

            

            #ifndef UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX
            //only defining to not throw compilation error over Unity 5.5
            #define UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input)
            #endif
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_instancing
            #include "UnityCG.cginc"
            #pragma shader_feature_local _SCREENSPACE_ON


            struct appdata
            {
                float4 vertex : POSITION;
                float4 color : COLOR;
                UNITY_VERTEX_INPUT_INSTANCE_ID
                
            };
            
            struct v2f
            {
                float4 vertex : SV_POSITION;
#ifdef ASE_NEEDS_FRAG_WORLD_POSITION
                float3 worldPos : TEXCOORD0;
#endif
                UNITY_VERTEX_INPUT_INSTANCE_ID
                UNITY_VERTEX_OUTPUT_STEREO
                float4 ase_texcoord1 : TEXCOORD1;
                float4 ase_texcoord2 : TEXCOORD2;
            };

            uniform float4 _Bottom;
            uniform float4 _Top;
            uniform float _mult;
            uniform float _pwer;

            
            v2f vert ( appdata v )
            {
                v2f o;
                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
                UNITY_TRANSFER_INSTANCE_ID(v, o);

                float4 ase_clipPos = UnityObjectToClipPos(v.vertex);
                float4 screenPos = ComputeScreenPos(ase_clipPos);
                o.ase_texcoord2 = screenPos;
                
                o.ase_texcoord1 = v.vertex;
                float3 vertexValue = float3(0, 0, 0);
                #if ASE_ABSOLUTE_VERTEX_POS
                vertexValue = v.vertex.xyz;
                #endif
                vertexValue = vertexValue;
                #if ASE_ABSOLUTE_VERTEX_POS
                v.vertex.xyz = vertexValue;
                #else
                v.vertex.xyz += vertexValue;
                #endif
                o.vertex = UnityObjectToClipPos(v.vertex);

#ifdef ASE_NEEDS_FRAG_WORLD_POSITION
                o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
#endif
                return o;
            }
            
            fixed4 frag (v2f i ) : SV_Target
            {
                UNITY_SETUP_INSTANCE_ID(i);
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(i);
                fixed4 finalColor;
#ifdef ASE_NEEDS_FRAG_WORLD_POSITION
                float3 WorldPosition = i.worldPos;
#endif
                float4 screenPos = i.ase_texcoord2;
                float4 ase_screenPosNorm = screenPos / screenPos.w;
                ase_screenPosNorm.z = ( UNITY_NEAR_CLIP_VALUE >= 0 ) ? ase_screenPosNorm.z : ase_screenPosNorm.z * 0.5 + 0.5;
                #ifdef _SCREENSPACE_ON
                float staticSwitch13 = ase_screenPosNorm.y;
                #else
                float staticSwitch13 = i.ase_texcoord1.xyz.y;
                #endif
                float4 lerpResult3 = lerp( _Bottom , _Top , pow( saturate( ( staticSwitch13 * _mult ) ) , _pwer ));
                
                
                finalColor = lerpResult3;
                return finalColor;
            }
            ENDCG
        }
    }
    CustomEditor "ASEMaterialInspector"
}

The error only occurs every second or third time I try to locally build the game.

However, when I am building with Unity Cloud Build it always appears.