Solaris?arnold glass shader issue using variant

[sami.tawil]

set up:
i have a usd file with many prim inside(glass models) which i bring in solaris to create variant.

On the left:

when applying transmission on variant arnold renders completely wrong, on the referenced file it is ok.

both network use the same material and render settings, and both prim are from the same original usd file
The glass acts as a closed shape. i tried editing normals but to no luck

On the right

Same setup but i use karma cpu instead of arnold, there is no issue with variant. 

 

[sami.tawil]

this is the solution renderGeometrysettings

add the specular transmit ray double sided. The question is why i do not need to add it on the  referenced network