When you have items on the ground and in inventory and try to craft all of them ground items disappear.

Reproduction:

1. Fill your inventory with some blocks, leave for example 5 slots open
2. Fill remaining slots with iron ingots or something that can be crafted into a block.
3. Drop another 4 stacks on the ground
4. Use crafting table while standing on the items
5. Shift click block crafting recipe twice rapidly. If it fails, click faster.
6. with succesfull reproduction the 5 stacks from your inventory are placed to first 5 slots of the crafting table in full stacks and dropped items have dissappeared.

Has happened in all 1.13+ versions.