Vray back to beauty advanced not working

Hi guys i am working on a project were we renderer all in multipass and the we are not being abble to rebuild the beauty, its always looking different do you have any idea on how to fix this?

Usualy we use quite simple operation multiply and plus in nuke. There is no secret, but now i already tried everything and is almost impossible to match.

Maybe there is something specific going on. Best you send the scene and image files so we can try to reproduce the issue.