Black Desert Online - The server stability is so awful that actual item duplication is possible.

Seems like Daum just can't get anything right. This works in NA and EU when it lags (which happens quite often). It does not work in Russia due to them having superior servers and less lag.

When the server lags to the point that you can open a single treasure chest multiple times before it disappears, you are ready to dupe (you actually sort of already did with the chest when you looted it twice). 

Put up an item on the marketplace and cancel it. Do this as fast as possible. Keep doing it until you dupe. Keep a close eye on your inventory while you are working on this.
It took me quite a few attempts, but I was able to dupe multiple items. It is much easier to do this with some sort of macro software, but entirely possible by hand.

Now, since it lags - there are actually two (and a half) chances to dupe. One when you are putting up the item (just keep spamming the conformation), and one when are taking off the item (just keep spamming the conformation).
This is where the half comes in - if you get your item back, but you still see it listed for sale - DO NOT try to get it back, as it will just disappear. BUT if you let it sell, you will get your money and whoever buys it will get a perfectly legit copy of the item. So don't get greedy and pass the love around.

It does not look like each item is assigned a unique ID, as I was able to sell and/or use my dupes. The duped items do not disappear after logging off. The exception to this rule was trying to get an item back that was still up for sale after going back into my inventory. So it looks like there is at least some minor kind of anti dupe in place.

Enjoy.

Got more fails for me? mmogfails@gmail.com