I have a problem about Substance In Unity Plugin.

Forgive my poor English.

Its the first time I use the substance in unity plugin.
When I import a sbsar file into unity , it creat a material with the standard shader inside by default,but I want to switch the standard shader to my custom shader,after that it will automatically fill some textures into the material texture propertie.

Thats cool, but the console window keep telling me "Material doesn't have a texture property '_BumpMap'" .

I try to fix it by going into the my shader file change the propertie name _NormalMap to _BumpMap. The error disappeared.

Inside the material, a normalMap the sbsar file generated fed into the texture propertie.
But when I want switch the normal map it fed into the texture propertie to another normap, It does not work .It always switch back to the normal map the sbsar file generated

How to fix to problem ?