"Sojourner of Malraxxus" reported as incomplete

On my character Hoazl@EU-Antonidas I finished the AV “Soujourner of Maldraxxus”, however in the API it is not reported as completed because criteria 88803 is reported as missing.

Endpoint: [eu.api…]/profile/wow/character/antonidas/hoazl/achievements?namespace=profile-eu&locale=en_US

Achievement ID: 14799

Response:

{
      "id": 14799,
      "achievement": {
        "key": {
          "href": "https://eu.api.blizzard.com/data/wow/achievement/14799?namespace=static-9.0.2_36532-eu"
        },
        "name": "Sojourner of Maldraxxus",
        "id": 14799
      },
      "criteria": {
        "id": 88794,
        "is_completed": false,
        "child_criteria": [
          {
            "id": 88795,
            "amount": 1,
            "is_completed": true
          },
          {
            "id": 88799,
            "amount": 1,
            "is_completed": true
          },
          {
            "id": 88803,
            "amount": 0,
            "is_completed": false
          },
          {
            "id": 88805,
            "amount": 1,
            "is_completed": true
          }
        ]
      },
      "completed_timestamp": 1606315760000
    },

(And yes the completed_timestamp is set but that is account-wide and I need the information on a per-character basis)

UPDATE (Dec 27th 2020): I just finished the quest a second time on this character and now the API also reports this achievement as completed. Funnily enough, I also got the message in-game that I got some “Achievement progress” (on the achievement I already completed on this character …).

=> Might be that I ran into a bug that has since been fixed and I needed to complete the quest after the fix for it to count
=> Might also be that the quest just has to be completed twice anyways