I'm sure someone has already found this exploit, but I still can use it in my version. Please patch it.

The bug (well, not a bug, an unpatched exploit) is that you can open a lootbag, optimally a legendary one, and leave a useless item in. You can then craft it back into four epic lootbags, craft those four back into the legendary lootbag, and get different loot every time. A simple fix for this would be to make a tag on the item that says it hasn't been opened, and require that for the crafting recipe.

Another note is I was using my own user-created modpack which uses version 1.10.2, and it uses the latest version of the modpack. I was using curse to launch and run my modpack. If you have fixed this in 1.11.2, please fix it in earlier versions, because many modpacks still use them.

Thanks,

--Cactus

Fixed a long time ago, in the general config find the option:
# If set to true, prevents bag crafting from working if any of the bags have been opened. B:"Prevent Merging Opened Bags"=false

and set it to true.