Uploading an update to a file with WriteMode.AsOverwrite mode with Id or Path fails

Hello.  I am using the .Net Dropbox.Api (6.37.0) with the following code sample:

using Dropbox.Api;
using Dropbox.Api.Files;
using System.Text;

namespace Dropbox
{
   internal class Program
   {
      static void Main(string[] args)
      {
         DropboxClientConfig config = new DropboxClientConfig
         {
            MaxRetriesOnError = 0
         };
         DropboxClient dropboxClient = new DropboxClient(AccessToken.ValidToken, config);

         Stream stream = new MemoryStream(Encoding.UTF8.GetBytes($"this is a test"));
         UploadArg uploadArg = new UploadArg($"/foo{Guid.NewGuid()}.txt"); // upload new file to root
         var result = dropboxClient.Files.UploadAsync(uploadArg, stream).Result;

         stream = new MemoryStream(Encoding.UTF8.GetBytes($"this is an updated test"));
         result = dropboxClient.Files.UploadAsync(result.Id, mode: new WriteMode().AsOverwrite, body: stream).Result;
      }
   }
}

 When running, the second UploadAsync throws an path/conflict/file exception.  This also repros if I change the first parameter in the second UploadAsync to result.PathLower.

Why is this?