No transparency featured in render(but alpha channels exist)

Hi,
I am trying to solve this riddle for long but all tips/manuals I ve found online didnt help.

When rendering via Vray (demo) transparency works well but in Kekrythea I'm dealing with problem of visible border of plants components (even though base pictures were saved with PS including alpha channels). I've checked on both -Pro 2015 and Made 2016 SU versions. Renders from both end up with lacking of transparency on components renders (unless prepated by Vray).

I ve always used Kerkythea (Vray is downloaded only for testing this issue) and never faced this problem before. Now even older .skp files (that have been working with Kerkythea properly in the past) dont have transparency on components neither.

I upgraded OS Win 8.1 to Win 10, is there any chance that OS upgrade could cause problem? I didnt find online anyone else asking this question before. Please let me know if you have any advice what to do (I'd rather use OS reinstalation as last possible option and frist try everything else).

I'm attaching files to clear up how my issue look like:)

make sure your .png is indeed perfectly transparent - zero pixels there.
you could maybe use smooth clipping in the material