SSHException Channel was closed intermittent behavior

We are connecting to a client SFTP and prior to this week had nothing but successful transactions.
We are now experiencing intermittent exceptions. We are calling this functionality from an Azure function, and the files are streamed from Azure storage, but i don't believe that has any impact on the issue.
I have tried both synchronous and asynchronous methods and had success locally, and on majority of live test cases, but when it fails, I don't have an idea of what the problem may be. Any thoughts would be much appreciated.

My code is below:

sftpClient.Connect();
var uploadPath = $"{sftpFolder}/{fileName}";
sftpClient.UploadFile(stream, uploadPath);
sftpClient.Disconnect();

Alternatively, I tried instead:

sftpClient.Connect();
var uploadPath = $"{sftpFolder}/{fileName}";
var returnVal = sftpClient.BeginUploadFile(stream, uploadPath, new AsyncCallback(x => FileTransferred(x, log, fileName, uploadPath)));

Commencez par les appels Connect(), UploadFile() et BeginUploadFile() signalés et comparez l’échec intermittent dans l’Azure Function avec les exécutions locales réussies. Capturez le contexte complet de la SSHException ainsi que les conditions de connexion ou de transfert ; le travail est considéré comme terminé lorsqu’une cause reproductible est identifiée et qu’une correction de la fermeture intermittente du canal est documentée ou validée.