Arimil

It seems this happens with anything in the reward block that changes the players inventory. I haven't found a workaround.

{
  "criteria": {
    "crafting_table": {
      "trigger": "minecraft:inventory_changed",
      "conditions": {
        "items": [
          {
            "item": "minecraft:crafting_table"
          }
        ]
      }
    }
  },
  "requirements": [
    [
      "crafting_table"
    ]
  ],
  "rewards": {
    "loot": [
      "test:diamond"
    ]
  }
}

{
  "type": "minecraft:advancement_reward",
  "pools": [
    {
      "rolls": 1,
      "entries": [
        {
          "type": "minecraft:item",
          "name": "minecraft:diamond"
        }
      ]
    }
  ]
}