Question I have to disable a keyword before enabling another one, why?

Can anyone help me with this one? I know there is scoring system behind how Unity select matching shaders, but I really can't figure out myself how that works under this situation.

Here is my key words set: _EMISSION _FOGENABLE _REALTIME_LIGHT_ENABLE _REFLECT_OFF _SOFTOUTLINE_ON _MY_FEATURE

To enable the keyword _MY_FEATURE at runtime in a build, I have to disable _FOGENABLE. Why is this happening? (I don't have to disable _FOGENABLE in editor mode tho)

 

Sure. The effect of _MY_FEATURE is enabled if I manually disable _FOGENABLE

Working:

Code (CSharp):

1.             var mat = GetComponent<MeshRenderer>().sharedMaterial;
2.             mat.EnableKeyword("_MY_FEATURE");
3.             mat.DisableKeyword("_FOGENABLE");

Not Working:

Code (CSharp):

1.             var mat = GetComponent<MeshRenderer>().sharedMaterial;
2.             mat.EnableKeyword("_MY_FEATURE");

Shader looks like this:

Code (CSharp):

1.             HLSLPROGRAM
2.             #include "../Library/Assets.hlsl"
3.             #pragma target 3.5
4.             #pragma prefer_hlslcc gles
5.             #pragma exclude_renderers d3d11_9x
6.             #pragma fragmentoption ARB_precision_hint_fastest
7.             #pragma skip_variants POINT POINT_COOKIE SHADOWS_SCREEN VERTEXLIGHT_ON LIGHTPROBE_SH SHADOWS_CUBE LINEAR_FOG
8.          
9.             #pragma multi_compile __ _DISABLE_FOG
10.             #pragma multi_compile __ LIGHTMAP_ON
11.             #pragma multi_compile __ _HEIGHTFOG_ON
12.             #pragma multi_compile _SOFT_SHADOW_16
13.             #pragma multi_compile __ _CASCADE_SHADOWMAP_ON _STANDARD_SHADOWMAP_ON
14.  
15.             #pragma shader_feature _REFLECT_OFF _REFLECT_CUBE _REFLECT_MIRROR
16.             #pragma shader_feature _RECEIVE_SHADOWS
17.             #pragma shader_feature _NORMALMAP
18.             #pragma shader_feature _RAMPMAP
19.             #pragma shader_feature _EMISSION
20.             #pragma shader_feature _FOGENABLE
21.             #pragma shader_feature _REALTIME_LIGHT_ENABLE
22.             #pragma shader_feature METALLIC_SPECGLOSS_MAP
23. #pragma shader_feature _ _MY_FEATURE
24.             #pragma vertex AssetsPassVertex
25.             #pragma fragment AssetsPassFragment
26.             ENDHLSL