https://www.youtube.com/watch?v=CYoFOP5OLCI

Yes another version for 1.7.10 is necessary

And it should not be major version 10 but 9.

@Eufranio Cannot reproduce in dev environment. Can you reproduce it in pure forge server or singleplayer?

Both singleplayer and multiplayer, using latest version from curse.

So is the steps like this below?

1. Place a hopper at top of cart dispenser to input the item stack to the dispenser
2. Give that dispenser a redstone signal
3. The dispenser still has the item in it while it spawns an item on the ground.

Does the size of the item stack matter? Or must you use hoppers to pick up items to dupe?

Okay, I made some other tests and I realized that the dupe happens only with the Draconic Chest, 3. The dispenser still has the item in it while it spawns an item on the ground.
The Cart Dispenser should accept only carts, right? Because we can't put items there, only trough cables/hoppers. The solution of the problem is simply block the item insert...

@Eufranio Can you dupe other items like Chaos shard, dragonic tools? Or try to dupe firestone from Railcraft?

It is probably because of custom item entities.

Should change this line from

EntityItem item = new EntityItem(worldObj, x + rx, y + ry, z + rz, cartStack);

to

Entity item = cartStack.getItem().createEntity(wordObj, new EntityItem(worldObj, x + rx, y + ry, z + rz, cartStack), cartStack);

Btw this need to be tested first.

You are right, I can dupe Firestone, Chaos Shards, Draconic Tools, etc.

@CovertJaguar Although the fix is found, but I think we need to provide a utility method to better process item dropping next time. I will work on fixing this later when I am home.

So can it replicate any item or just that dragonic evolution chest? Those hoppers are vanilla ones right?

Yes, they are vanilla ones. It can dupe everything, normal items, NBT-filled items, blocks, etc.

Fixed for 10.0.0

Can you backport the fix for 1.7.10?

@Eufranio For now, I suggest you ban cart/train dispenser.

It's banned since I reported this dupe, but I would like unban it, it's a cool block =/