Just started to play the FTB Revelation pack and was using the dank null for mining when i noticed this duplication bug.

So far was able to replicate with any stack able item in the game.

I only noticed this on the Emerald level of the dank null have not tested on lower levels.

its not a fast dupe but its a dup none the less...

Steps to replicate.
-Have a stack of 3 items in any dank null slot
-right click to take half a stack out. you end up with 2 item on your cursor and 2 in the slot.
-put 1 item into your player inventory and put 1 back into the dank null and you are back to 3.
-repeat

I followed the steps on a singleplayer mode in FTB Revelations and it worked.
I followed the steps with the /Dank/Null mod by itself in a singleplayer world with the latest version it did not work. Possibly, the modpack you are using has the mod outdated for its version.

Nonetheless, great discovery!

Outdated version and very similar issues fixed in #263 Open new bug using version past that if still persists.