Not able to get the GetGuestNetworkPassword trait work on the router device

Question

I'm currently working on integrating my FritzBox router with the Google Smart Home App. I've successfully connected various local devices, such as my computer as a Gameconsole, to the app using an API on my NAS.

The integration is working smoothly for all functionalities, including enabling/disabling the guest network, speed tests, etc. However, I'm encountering an issue with the GetGuestNetworkPassword command.

Problem Description: When I attempt to access the guest network settings on my Google Nest Hub 2 device, I get prompted to enter my PIN. After entering the PIN, the loading square appears, the guest network password as a QR code should be displayed. Unfortunately, the loading never completes.

Request and Response Details:

1. SYNC Response:

{
  "requestId": "4186254821521734737",
  "payload": {
    "agentUserId": "00000",
    "devices": [
      {
        "type": "action.devices.types.ROUTER",
        "traits": [
          "action.devices.traits.NetworkControl",
          "action.devices.traits.SoftwareUpdate",
          "action.devices.traits.Reboot"
        ],
        "name": {
          "name": "Router"
        },
        "willReportState": true,
        "notificationSupportedByAgent": false,
        "deviceInfo": {
          "manufacturer": "AVM",
          "model": "7580",
          "swVersion": "7.30"
        },
        "attributes": {
          "supportsEnablingGuestNetwork": true,
          "supportsDisablingGuestNetwork": true,
          "supportsGettingGuestNetworkPassword": true,
          "supportsEnablingNetworkProfile": false,
          "supportsDisablingNetworkProfile": false,
          "supportsNetworkDownloadSpeedTest": true,
          "supportsNetworkUploadSpeedTest": true
        },
        "id": "125823037498738",
        "customData": {}
      }
    ]
  }
}

2. QUERY Response:

{
  "requestId": "9323250515783345712",
  "payload": {
    "devices": {
      "125823037498738": {
        "status": "SUCCESS",
        "online": true,
        "lastSoftwareUpdateUnixTimestampSec": 1702263739,
        "networkEnabled": true,
        "networkSettings": {
          "ssid": "Martin Router King"
        },
        "guestNetworkEnabled": true,
        "guestNetworkSettings": {
          "ssid": "Martin Router King Gast"
        },
        "numConnectedDevices": 0,
        "networkUsageUnlimited": true,
        "lastNetworkDownloadSpeedTest": {
          "downloadSpeedMbps": 71.80409032702916,
          "unixTimestampSec": 1702242312,
          "status": "SUCCESS"
        },
        "lastNetworkUploadSpeedTest": {
          "uploadSpeedMbps": 29.22374429223744,
          "unixTimestampSec": 1702242312,
          "status": "SUCCESS"
        },
        "networkSpeedTestInProgress": false
      }
    }
  }
}

3. First Request (without challenge):

{
  "inputs": [
    {
      "context": {
        "locale_country": "DE",
        "locale_language": "de"
      },
      "intent": "action.devices.EXECUTE",
      "payload": {
        "commands": [
          {
            "devices": [
              {
                "customData": {},
                "id": "125823037498738"
              }
            ],
            "execution": [
              {
                "command": "action.devices.commands.GetGuestNetworkPassword",
                "params": {
                  "followUpToken": "0025f6b7588f61c3fd76bb50cb7191a0b122b5eab2e8a66d10045cc26c28f39c9f6c500ae6607609544cfd52b12fa0ff279fb61f1964"
                }
              }
            ]
          }
        ]
      }
    }
  ],
  "requestId": "4461519532043804226"
}

Response:

{
  "requestId": "4461519532043804226",
  "payload": {
    "commands": [
      {
        "ids": [
          "125823037498738"
        ],
        "status": "ERROR",
        "errorCode": "challengeNeeded",
        "challengeNeeded": {
          "type": "pinNeeded"
        }
      }
    ]
  }
}

4. Request with Challenge:

{
  "inputs": [
    {
      "context": {
        "locale_country": "DE",
        "locale_language": "de"
      },
      "intent": "action.devices.EXECUTE",
      "payload": {
        "commands": [
          {
            "devices": [
              {
                "customData": {},
                "id": "125823037498738"
              }
            ],
            "execution": [
              {
                "challenge": {
                  "pin": "PIN"
                },
                "command": "action.devices.commands.GetGuestNetworkPassword",
                "params": {
                  "followUpToken": "0025f6b7587cd68de9c2fd3e5bdd89dda696eec72cbda421b0afb4eb777c45f9daba3fb4ee441a23b001ad42719440300ffd5a6fee31"
                }
              }
            ]
          }
        ]
      }
    }
  ],
  "requestId": "4461519532043804226"
}

Response:

{
  "requestId": "4461519532043804226",
  "payload": {
    "commands": [
      {
        "ids": [
          "125823037498738"
        ],
        "status": "SUCCESS",
        "states": [
          {
            "guestNetworkPassword": "PASSWORD"
          }
        ]
      }
    ]
  }
}

5. Cloud Console Log:

{
  "data": {
    "executionLog": {
      "executionResults": [
        {
          "actionResults": [
            {
              "device": {
                "deviceType": "ROUTER"
              },
              "action": {
                "actionType": "NETWORKCONTROL_GET_GUEST_NETWORK_PASSWORD",
                "trait": "TRAIT_NETWORK_CONTROL"
              },
              "status": {
                "isSuccess": false,
                "statusType": "CHALLENGE_NEEDED"
              }
            }
          ],
          "executionType": "PARTNER_CLOUD",
          "latencyMsec": "112",
          "requestId": "4461519532043804226"
        }
      ]
    },
    "locale": "de-DE"
  }
}

I'm not sure if the Cloud Log is even relevant because I have implemented the challenge as you can see.

I've already tried to add the followUpToken to the commands body in the response. Also I tried to add some of the QUERY response states like the SSID of the guest network to the state body of the GetGuestNetworkPassword command.

Am I missing something in the implementation, or is there a different approach I should take?