The bug

While modifying the inventory updates recipe availability, modifying the crafting grid does not.

Symptoms

As shown in the video; this bug causes recipes to show as unavailable if all the materials are manually moved out of the inventory and into the crafting grid. Taking the materials out of the inventory makes the recipe unavailable, but placing them into the crafting grid doesn't update the recipe as available.

Manually updating the inventory will cause the availability to update correctly, counting the crafting grid along with the inventory as expected.

You can trigger an update by picking up or placing down some item in the inventory - I used planks in the video.

Video

• Note how lifting the leather out of the inventory causes the recipe to become unavailable (expected)
• However, placing it into the crafting grid doesn't cause the recipe to become available (bug)
• Manually updating the availability (using planks) causes the recipe to become available again
• Lifting the paper out of the inventory doesn't make the recipe unavailable, since some other paper is still in the crafting grid when the update occurs
• Using the recipe book to move items into the crafting grid doesn't make recipes unavailable (since the items are are never picked up by the mouse and never "hovering" out of inventory/crafting grid)

Implications

This means that if all the materials have been placed into the crafting grid, you cannot use MC-117580 to rearrange them (without first manually updating the availability) since the grid will be emptied if you click on an unavailable recipe.