Solution
I kind of fixed it :) Will overwrite my fix every time it is opened in ShaderForge, but worth checking out.
Having exactly the same problem, I wonder if Unity have changed the CGIncludes from UnityPBSLighting and UnityStandardBRDF?
Solution
Corrigé
This has now been fixed in 1.26, which is now also released :)
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This has now been fixed in 1.26, which is now also released :)