When crafting items with a full inventory, it is possible to lose the crafted items. AKA they get deleted after being crafted. This is a massive flaw in the crafting system, and can result in up to a 90% loss in crafted items, especially for those on windows 10 who are mass crafting. Mass crafting being where you break double chests full of items to craft them. Melon slices to melons for example.
It only happens in a specific way, and its rather hard to explain in text, so i'll just link to the bugrock of the week video i did on this, which shows how to reproduce 100% of the time.
Steps to reproduce:
1. In Creative mode, place a full stack of oak planks in your inventory. Fill the rest of your inventory with wooden shovels.
2. Switch to Survival mode.
3. Open a crafting interface (either the player's inventory or a crafting table).
4. Locate the recipe for oak slabs in the recipe book and shift-click it. This will leave a stack of 60 oak slabs attached to the cursor because there is no room to store it in the player's inventory.
5. Shift-click the oak slab recipe a second time.
Uncertain. The excess items should probably be thrown on the ground, since there's nowhere to put them. They could also be put in the crafting grid if there's a place for them, but once the grid is full the same problem arises.
The ingredients are consumed but no output items are produced and stored.