No records found -500 Internal Server Error

Hi experts,
I have wrote the C# API programe to get data from different location.
All used to work fine.Suddenly it's generating error becuase the records not available
in the API records.(requesting records)There is no way to find Candidate avaiable or not.

see below link how the API request send.

https://test/v3/company/18f62e940d1d01/position/771b0f2aff3c01/candidate/05ea659e456a01/stream

Error:

 500 Internal Server Error
{
    "error": {
        "type": "getStreamError",
        "message": "there was an unknown error getting candidate stream."
    }
}

 string urlCandatestream = "/company/" + CompanyID + "/position/" + positionID + "/candidate/" + candidateID + "/stream";
                var request = new RestRequest(urlCandatestream, Method.GET);


                request.AddHeader("Content-Type", "application/json");
                request.AddHeader("cache-control", "no-cache");
                request.AddHeader("authorization", connectAPI.getAccessToken());
                // rqst.Proxy = GlobalProxySelection.GetEmptyWebProxy();

                IRestResponse response;
                varRequest = request.ToString();
                try
                {
                    response = await _restClent.ExecuteTaskAsync(request);
                    VarRequestResults = response.Content;
                }
                catch (Exception ex)
                {
                    throw new Exception("Error executing  request to " + urlCandatestream, ex);
                }

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Any logic or idea how to get rid of this and only get available records.