When I use Duplicate on a Camel Train, I gain a second Camel Train, which means I should exile a second gold. It only exiled one gold.
Thanks for the report, RiverOfRationality!
I just checked this, and it seems to work. Do you have the game number of that game, so I can check if some special circumstances lead to that bug? If not, if it was a rated game if you give me your in-game name I might be able to find the game ID myself.