Example of the bug: you have 2 slots available in your inventory and there are 3 stacks of iron ingots on the floor, you will pick up 2 stacks of the iron ingots and there will be 1 stack on the floor, then you shift click on iron block in the recipe book, then you will pick up the 1 stack of iron ingots from the floor, then you shift click on iron block in the recipe book again, then you exit the inventory without crafting the iron blocks and you will only get the iron ingots back that fit in your inventory - in this case 2 stacks, the others will not drop on the floor. So you lost 1 stack of iron ingots in this case.