Why is Graph QL returning data that is clearly NOT fulfilling the request condition?

To mark which orders are already handled we tag them with a “fetched” tag and we already have hundreds of those. To request “unfetched” orders we use the following GraphQL query:

{
  orders(first:250 query:"NOT tag:fetched") {
  	edges{
      node{
        id
        tags
      }
    }
  }
}

works fine, but today we get the following response (one order!). note the “fetched” Tag

"data": {
    "orders": {
      "edges": [
        {
          "node": {
            "id": "XXXXXXXX",
            "tags": [
              "fetched"
            ]
          }
        }
      ]
    }
  }

It was solvable by adding and removing a random tag to and from the order, but what??? Do we have to account for the API not working as instructed?

What the hell? it happened again, this time big time (about 20 orders). Has anybody (especially Shopify-Staff) any explaination for this??

We should be able to rely on GraphQL results, when we request NOT tag:fetched the result should be orders WITHOUT the tag “fetched”!