How ist transparency handled in Hypersnap?

When I render a product-shot out of SolidWorks as *.png with 16bit I get a picture with transparent background.
When I load the picture everything is fine and transparent as it should be.
I add some labels and save out of Hypersnap the edited image with transparent option on but when I reopen the modified file, there are some more areas transparent inside the object for example where some highlight reflections are rendered on the object.
Also if I crop an area, or select a region and do a copy/paste into another picture all the former transparent areas turn into white.
 
So my question is how does Hypersnap internally is handling files with 8bit transparency?
Ist there a way with the actual version to keep this thransparency through editing and get  good results? Any tips for a workaround?
On my desired features wishlist in Hypersnap, correct handling of 16bit *.png image files with transparency is on very, very very top row.
 
greetings from Austria
Alex