Getting SharePoint Managed Metadata Fields via Graph API

[M-Patrone]

I'm running into an issue with the Microsoft Graph API and could really use some help.

I'm trying to retrieve the value of a managed metadata field from a SharePoint list item. When I execute the following request on my test SharePoint environment, everything works fine and I receive the expected metadata (also Term value):

Request:

https://graph.microsoft.com/v1.0/sites/test.sharepoint.com,c**************/lists/************/items/46/fields?$select=Categori

and production url:

https://graph.microsoft.com/v1.0/sites/prod.sharepoint.com,0**************/lists/********************/items/22292/fields?$select=Client

Response (for demo the Graph Explorer used):

{
    "@odata.context": "***************",
    "@odata.etag": "***********",
    "@microsoft.graph.tips": "Use $select to choose only the properties your app needs, as this can lead to performance improvements. For example: GET sites('<key>')/lists('<guid>')/items('<key>')/fields?$select=id",
    "Categori": [
        {
            "Label": "Anleitungen",
            "TermGuid": "508ba****************",
            "WssId": 1
        }
    ]
}

However, when I try the same request in the production environment, targeting a different metadata field (named Client), the field is always returned empty, even though it has a value in the SharePoint UI.

Response in production:

{
  "AdditionalData": {
    "@odata.context": "***************",
    "@odata.etag": "****************",
    "Client": {}
  },
  "BackingStore": {
    "ReturnOnlyChangedValues": false,
    "InitializationCompleted": true
  },
  "Id": null,
  "OdataType": null
}

A few additional details:

• The Client field in production is a single-value managed metadata field (unlike Categori in test, which is multi-value). But I also tried when Client is set to multi-value.
• I’ve tried various combinations of $select and $expand, but the result is always the same.
• Interestingly, I can successfully update the Client field from the c# application using the guidance from this StackOverflow post, so write access works.
• Other custom fields (non-managed metadata) return values correctly.
• I'm using the Microsoft Graph SDK for .NET (Microsoft.Graph version 5.56.0).

and the request is made like that:

   var result = await graphServiceClient.Sites[siteId].Lists[listId].Items[listItemId].Fields.GetAsync((requestConfiguration) =>
                    {
                        requestConfiguration.QueryParameters.Select = new string[] { "client" };
                    });

Has anyone experienced a similar issue where a managed metadata field (especially a single-value one) returns an empty object when reading through Graph API, despite having a value?

Any ideas on what could be wrong or what else I could try?

Thanks in advance!