Steps to reproduce:

1. While in Survival mode, enter the Crafting Table interface.
2. Search or seek the Dispenser item from the recipe book.
3. Click on it to auto-populate the Dispenser recipe into the 9x9 crafting grid...
4. However, the Dropper recipe populates and a Dropper item will be crafted (a Bow in your inventory is not placed into the 9x9 grid and is not consumed).

Clicking on the Dispenser item multiple times will not increment the number of Droppers created (even if multiple materials needed are present in the player inventory), but you can click the Dispenser and then the Dropper from the recipe book to create two Droppers.