Intermittent Worldcheckone server connection issue

2% to 3% of total portal worldcheckone call/requests are getting failed with below connection issues to dev worldcheckone server

• Unable to connect to the remote server
• The underlying connection was closed: An unexpected error occurred on a receive.
• The underlying connection was closed: A connection that was expected to be kept alive was closed by the server.
• The remote server returned an error: (503) Server Unavailable.
• The remote server returned an error: (400) Bad Request.

Is there any known solution for this type of connection issues?

Below is the sample code snippet for call/request

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string date = dateValue.ToString("R"); // WC1 header requires GMT datetime stamp

string requestendpoint = "https://" + GateWayHost + GateWayUrl + "cases/" + CaseSystemID + "/screeningRequest";

string postData = "{\"customFields\":[],\"providerTypes\":[\"WATCHLIST\"]}";

string msg = postData;

string dataToSign = "(request-target): post " + GateWayUrl + "cases/" + CaseSystemID + "/screeningRequest" + "\n" +

"host: " + GateWayHost + "\n" + // no https only the host name

"date: " + date;

string hmac = generateAuthHeader(dataToSign, APISecret);

string authorisation = "Signature keyId=\"" + APIKey + "\",algorithm=\"hmac-sha256\",headers=\"(request-target) host date\",signature=\"" + hmac + "\"";

//Defining TLS

ServicePointManager.Expect100Continue = true;

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls

| SecurityProtocolType.Tls11

| SecurityProtocolType.Tls12

| SecurityProtocolType.Ssl3;

//END

// Send the Request to the API server

HttpWebRequest WebReq = (HttpWebRequest)WebRequest.Create(requestendpoint);

// Set the Headers

WebReq.Method = "POST";

WebReq.Headers.Add("Authorization", authorisation);

WebReq.Headers.Add("Cache-Control", "no-cache");

WebReq.Date = dateValue; // use datetime value GMT time

using (HttpWebResponse WebResp = (HttpWebResponse)WebReq.GetResponse())

{ // Status information about the request

if (WebResp.StatusCode.ToString() == "Created")

{

str = WC1CaseAuditEventRequest(requestObj, request, calledBy, quoteId, historyId, partyType, CaseSystemID, dateValue);

}

}

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