If say I need oak slabs and I have oak logs I convert all to planks and then slabs by clicking multiple times in the Recipe Book, but say I don't have the inventory room for all the slabs or items that I am creating, then a stack or how ever number will then appear in my hand and will not drop. If  I close the crafting table then any time I open my inventory, those items are still present and I can't rearrange my inventory because those items won't drop. I have to log out of the game and come back in to get it to correct itself. This happens with the solo game as well as the Realm. I have only tested it with the logs to planks and planks to slabs, but assume it is happening to other items as well.