I tried two series of attempts to use Duplicate. 9 times on Booty Master and 6 times on Master Craftsmanship. Every time failed. It was reported to me as being broken before I tried it.

I am sorry to report that Duplicate did work for me 4 out of 5 times.

Still worth checking the random generator formula that nothing is interfering with a fair result.

It is just totally random; no control over the dice. Its pure luck. It imitates the coin flip.
Same goes for other such cards, such as Death poker.

You have just been too unlucky.

I've used Death Poker about 12 times and it only worked twice. I must be unlucky too.

Death Poker worked only 20% of the time for me so far.

My Duplicate cards always fail with Booty master but successful with other cards. Anyone has this problem?

Short version:
You lost the flip!

Long version:
These conspiracies theories are inexistent.

Duplicate works exactly like many other chance features in the game (ie Mindbar).
Here is a page to test your theories:
http://s2.piratesglory.com/dice.php
Pretend you are going to cast Duplicate every time you click Roll Again.

For any number of 50 or more, Duplicate is successful. For any number less than 50, duplicate fails.

Thanks. I just find it curious that I am never successful with that one card though. I am successful with the others though.
I tried the link. I was successful most of the time.

It's pure luck.

Works for me 100% of the time, when it fails I forget that it's 50/50 and think it's a glitch. Same thing with mindbars, i get the down in the first 3 times, my new name shall be lucky roi