Strange error for no reason when using CSOM C# API

Question

I am using the SharePoint 2016 C# CSOM SDK to create a subsite in a site collection (code below). However, I get this error:

at Microsoft.SharePoint.Client.ClientRequest.ProcessResponseStream(Stream responseStream) at Microsoft.SharePoint.Client.ClientRequest.ProcessResponse()

The code does work and the site gets created, but I don't know what the error is?

Code:

                ClientContext context = new ClientContext(sp2016url);
                WebCreationInformation creation = new WebCreationInformation();             
                creation.WebTemplate = "{9D2F0ED0-8EAC-4E22-83D5-B44E5F2AED85}#legnewtemplate";
                creation.Url = GetIDFromKey(legdata.file_reference); 

                creation.Title = "Site";
                creation.Language = 1033;
                creation.UseSamePermissionsAsParentSite = true;
                Web newWeb = context.Web.Webs.Add(creation);

                NetworkCredential cred = new NetworkCredential(@"xxxxx", "xxxxx", "xxxx");
                CredentialCache cache = new CredentialCache();
                cache.Add(new Uri(sp2016url), "NTLM", cred);

                context.Credentials = cache;
                // Retrieve the new web information. 
                context.Load(newWeb, w => w.Title);
                context.ExecuteQuery();

Answer 1

Please try this Code:

                ClientContext context = new ClientContext(sp2016url);
                NetworkCredential cred = new NetworkCredential(@"xxxxx", "xxxxx", "xxxx");
                CredentialCache cache = new CredentialCache();
                cache.Add(new Uri(sp2016url), "NTLM", cred);
                context.Credentials = cache;

                WebCreationInformation creation = new WebCreationInformation();             
                creation.WebTemplate = "{9D2F0ED0-8EAC-4E22-83D5-B44E5F2AED85}#legnewtemplate";
                creation.Url = GetIDFromKey(legdata.file_reference);                    

                creation.Title = "Site";
                creation.Language = 1033;
                creation.UseSamePermissionsAsParentSite = true;
                Web newWeb = context.Web.Webs.Add(creation);
                context.ExecuteQuery();

                // Retrieve the new web information. 
                context.Load(newWeb, w => w.Title);
                context.ExecuteQuery();