Minor difference in alpha output from refracted material between RT gpu and RT cpu .
I believe cpu is correct.
Both alphas seems identical on our side, can you share the scene?
Thank you for sending the scene. Both of the issues are now logged in the bug tracking system.
About the refraction mismatch: V-Ray GPU uses the min of the Max depth value in the material itself instead of the Trace depth.
We are investigating the Alpha issue.