This bug caused some really big problems. I am of course talking about the bug, that caused the CustomCrafting GUI to not work properly. If more than 1 player was online you were able to take out the GUI items, which is no good.
My first thought was that it's caused by processing speed, but as it turned out, it wasn't that.
So, it should all be fixed now. If you still encounter this bug, please let me know. Fastest way is to let meknow on my Discord server
With this update you should be able to use the CustomCrafting GUI properly again.
It should be noted that if two players are editing the same recipe at once it may cause some problems!
However, I am still rewriting the Invenory API to improve it's performance. But this will take time.