I was messing around with the new smithing table recipes for datapacks, and found that when you double click to collect items in your inventory, it creates 2 of the the output items from the smithing table.
Here is a video of the problem: https://youtu.be/XuPbKD5782c

Here is the json used for the recipe:

{  "type": "minecraft:smithing",  "base": {    "item": "minecraft:iron_block"  },  "addition": {    "item": "minecraft:diamond"  },  "result": {    "item": "minecraft:diamond_block"  }}

EDIT:

This has a more serious bug where it will delete output result items when there is a "count" on the result item, and it reaches a full stack size, shown in this video:
https://youtu.be/aD7Qt64zvt4

Using this json:

{  "type": "minecraft:smithing",  "base": {    "item": "minecraft:iron_block"  },  "addition": {    "item": "minecraft:diamond"  },  "result": {    "item": "minecraft:diamond_block",    "count": 3  }}