Double-clicking on touch controls acts like shift-clicking in java all the time so when a crafting recipe is crafted and clicked twice it crafts the maximum amount of the recipe from your inventory can get. Example, crafting sticks, I just want 12, but I clicked twice too fast, I have 16 planks, so it crafts 32.
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We're tracking this issue in MCPE-163736, so this ticket is being resolved and linked as a duplicate.
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