C# Lambda can't read from DynamoDB

I have a method:

{
public const string TableName = "tableName"

...

public static async Task<Data> Load(AmazonDynamoDBClient dynamo, string sName)
    {
      Data data = null;

      GetItemRequest request = new GetItemRequest
        {
          TableName = TableName,
          Key = new Dictionary<string, AttributeValue>
                {
                  { "Name", new AttributeValue { S = sName } }
                }
        };
   
      try
      {
        GetItemResponse getDataResponse = await dynamo.GetItemAsync(request);
       
        if (getDataResponse!= null && getDataResponse.Item != null)
        {
          data = new Data(sName, getDataResponse.Item);
        }
        else
        {
          Console.WriteLine("No data in dynamo");
          throw new Exception($"Unable to load data '{sName}' from table '{TableName}'!\nThe data was not found");
        }
      }
      catch (Exception ex)
      {
        Console.WriteLine($"Stack trace: {ex.StackTrace}");
        throw new Exception($"Unable to load data '{sName}' from table '{TableName}'!\n" + ex.Message, ex);
      }

      return data;
    }
}

That when called, is only available to retrieve the data from the DynamoDB table approx. 50% of the time.

That it works some of time makes me confident that permissions and networking are configured correctly.

I have implemented a 'keep warm' event via EventBridge to try and mitigate cold starts, to no avail. The AmazonDynamoDBClient is instantiated as a field on a separate class, the lambda itself, that calls this method, prior to the function handler being called. Looking something like this:

public class LambdaFunction
{
    private Dynamo.Data data = null;
    private AmazonDynamoDBClient dynamo = new AmazonDynamoDBClient()

    private async Task FunctionHandler(event, context)
    {
        // event validation ...
        await ProcessData(dynamo, event.data);
    }

    public async ProcessData(AmazonDynamoDBClient dynamo, OtherClass.Data data)
    {
        Namespace.Class data = await Namespace.Class.Load(dynamo, data.name);              // Load() method above
        // processing of data
        return data;
    }
}

I can't see any throttled requests on the table and no exceptions are being thrown in the lambda logs. I've tried extending the lambda processing time and available memory but that doesn't help.

Any advice is greatly appreciated.