Error Uploading When Using ListData.svc and HTTPS

Question

SharePoint 2016 on premise
Site Collection admin
Using ListData.svc, I can create list items.
Exact code works with SP10 with no errors.
Using the code below, I'm able to upload a file, but I'm receiving an error.

string sharePointSvc = "https://sp2016.some.url/sites/random/_vti_bin/ListData.svc";

            using (FileStream file = File.Open(@"C:\test1.docx", FileMode.Open))
            {
                ServRef.RandomDataContext ctx = new ServRef.RandomDataContext(new Uri(sharePointSvc));

                ctx.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;

                string filename = Path.GetFileNameWithoutExtension(file.Name);
                string path = "/sites/random/dropofflibrary/" + Path.GetFileName(file.Name);
                string contentType = "Interest Summary";

                ServRef.DropOffLibraryItem documentItem = new ServRef.DropOffLibraryItem()
                {
                    ContentType = contentType,
                    Name = filename,
                    Title = filename
                };

                ctx.AddToDropOffLibrary(documentItem);
                ctx.SetSaveStream(documentItem, file, false, contentType, path);

                try
                {
                    ctx.SaveChanges();
                }
                catch (Exception ex)
                {
                    var err = ex.Message;
                    throw;
                }
            }    

Errors
Output error: An error occurred while processing this request.

Errors from Fiddler:
Auth:
No Proxy-Authenticate Header is present.

No WWW-Authenticate Header is present.

Caching:

Under RFC2616, HTTP/500 responses will not be cached regardless of what caching headers may be present. HTTP/1.1 Cache-Control Header is present: no-cache

This response does not specify explicit HTTP Cache Lifetime information and does not specify a Last-Modified date. Heuristic expiration is typically based on Last-Modified date. Lacking Last-Modified, this response may be revalidated on every use or once per browsing session, depending on the browser configuration.

This response contains neither an ETAG nor a Last-Modified time. This will prevent a Conditional Revalidation of this response.

Answer 1

Including the Path property fixed the issue I was having.

ServRef.DropOffLibraryItem documentItem = new ServRef.DropOffLibraryItem()
{
        Path = path,
        ContentType = contentType,
        Name = filename,
        Title = filename
};