Updating old shader to newer lightmapping

I have some art content that was made back for Unity 5 and from 2017+ the lightmapping bakes shadows to the wrong faces, I believe the uv's for the lightmap are either reversed from how it used to be, or the uv channel for lightmapping changed between Unity 5 and modern versions?

Example:
The shadows are on the top rather than around the base. The shadow that rock is in is created from a cookie on the directional light.





The shader was using the following:

Code (CSharp):

1. v2f vert (appdata v)
2.             {
3.                 v2f o;
4.                 o.vertex = UnityObjectToClipPos(v.vertex);
5.                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
6.                 UNITY_TRANSFER_FOG(o,o.vertex);
7.                 o.uv2 = v.uv2.xy * unity_LightmapST.xy + unity_LightmapST.zw;
8.                 o.uv3 = TRANSFORM_TEX(v.uv, _Tex1);
9.                 o.uv4 = TRANSFORM_TEX(v.uv, _Tex2);
10.                 o.uv5 = TRANSFORM_TEX(v.uv, _Tex3);
11.                 o.color = v.color;
12.                 return o;
13.             }
14.          
15.             fixed4 frag (v2f i) : SV_Target
16.             {
17.                 // sample the texture
18.                 fixed4 col = tex2D(_MainTex, i.uv);
19.                 col.rgb *= 1.0-saturate(i.color.r + i.color.g + i.color.b); // the inverse of all other info
20.  
21.                 fixed4 splat1 = tex2D(_Tex1,i.uv3) * i.color.r;
22.                 fixed4 splat2 = tex2D(_Tex2,i.uv4) * i.color.g;
23.                 fixed4 splat3 = tex2D(_Tex3,i.uv5) * i.color.b;
24.                 col.rgb += splat1.rgb + splat2.rgb + splat3.rgb;
25.                 col.rgb = saturate(col.rgb);
26.              
27.                 #ifdef LIGHTMAP_ON
28.                     fixed3 lm = DecodeLightmap(UNITY_SAMPLE_TEX2D(unity_Lightmap,i.uv2)).rgb;
29.                     col.rgb *= lm;
30.                 #endif
31.              
32.                 // apply fog
33.                 UNITY_APPLY_FOG(i.fogCoord, col);
34.  
35.                 col.a = 1.0;
36.                 return col;
37.             }