Sporadic connection when using OpenEdge.Net.HTTP

Hi All

Please forgive the potentially stupid question but I'm a bit lost, and I'm hoping someone could point me in the right direction.  I'm trying to do a POST request using the OpenEdge.Net.HTTP library on OE 11.6.3, but when running through the procedure editor it will connect some of the time, and then refuse the connection with the following error:

SSL failure. Error code 10057: Unknown network error (9318).

It will then return this error the next few times I run the code, and then mysteriously connect again.  If I use HttpMaster to test the request then it works consistently.  It's only with this particular web service, as all my other connections using the library are fine.  

My code is as follows:

oLib = ClientLibraryBuilder:Build() 
                           :sslVerifyHost(NO) 
                           :Library. 
//Build request 
oRequest = RequestBuilder:Post("training.link.com/.../Test", oRequestBody) 
                         :ContentType(ipContentType) 
                         :AddHeader(cHeaderName, cHeaderValue) 
                         :AcceptXML() 
                         :Request.

//Send the request 
oResponse = ClientBuilder:Build() 
                         :UsingLibrary(oLib) 
                         :Client:Execute(oRequest).

Any assistance would be much appreciated.

Regards,

Catherine