BigBlueButton : Error While Copying Content to a Stream

Question

I Recently Started A Project Which Works With BigBlueButton APIs and Have A Controller With This One of Main Actions For Creating and Start a new Meet in BBB :

 [HttpPost("[action]")]
    public async Task<IActionResult> CreateMeeting([FromBody] CreateMeetingRequestModel request)
    {
        var result = await _client.CreateMeetingAsync(
            new CreateMeetingRequest
            {
                name = request.Name,
                meetingID = request.MeetingId,
                record = true
            }
        );
        if (result.returncode == Returncode.FAILED)
            return BadRequest("A Problem Has Been Occurred in Creating Meet.");

        System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
        xmlDoc.LoadXml(result.ToString());
        string jsonResult = JsonConvert.SerializeXmlNode(xmlDoc, Formatting.Indented, true);

        return Ok(jsonResult);
    }

When I Need To Start it With Swagger And Create A Class :

But This Error Has Been Occurred :

My Reference in Project :

BigBlueButtonAPI.NET

May This Error Because of BBB Server ?