I've been trying to convert our Uber shader to work in 9.5
After sorting out all the “fit range” errors (due to missing clamp parm), and finding it still not working, I finally narrowed it down to having string channel references as the default value on some Parameters.

These channel references exist because several of the shaders features such as occlusion object masks, reflection masks, light masks etc, are linked to another asset that serves the purpose of controling these parameters without the hassle of having to go into each and every shop to change them.
non-string references still work fine (used for things like occ/reflection samples).

cheers
Serg