In the crafting screen you're able to stack things on top of each other. It took me a very long time to figure out that this is NOT how you craft things, but rather you have to mash stuff together with the action button in the short time before it slips out of your hand...
To reproduce: Grabs something, move near something else, wait for the item to slip out of your hand. Press in the direction of the other thing and hit the action button, it pulls it into the current tile.
