Antwoord

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?

Antwoord
Fixed
This has now been fixed in 1.26, which is now also released :)
Customer support service by UserEcho
This has now been fixed in 1.26, which is now also released :)