Hi Hevedy,
Thank you for reporting this issue. It has already been logged with ticket UE-1169, although this issue is currently backlogged and will be resolved at a later date. There is no timeframe for when this will be worked on though.
This is the original post that the issue was reported with: Can you copy primitives after you Flip them in the Geometry Editing Mode? - Programming & Scripting - Epic Developer Community Forums
Thank you!
Tim