1. Download the attached datapack, bug.zip
2. Note that this datapack includes a single recipe, 7 chains to chainmail leggings that stack to 64.
3. Craft this recipe once to unlock it in the recipe book.
4. Then attempt to craft two of these stackable chainmail leggings by clicking twice on the recipe in the recipe book.

Clicking the recipe twice only moves enough ingredients for one pair of chainmail leggings, instead of moving enough for two.

Shift-clicking the recipe only moves enough ingredients for one pair, rather than all possible ingredients.

This does not affect shapeless recipes.