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)));

Iniziare con le chiamate Connect(), UploadFile() e BeginUploadFile() segnalate e confrontare il malfunzionamento intermittente nell’Azure Function con le esecuzioni locali riuscite. Acquisire il contesto completo della SSHException e le condizioni di connessione o trasferimento; il lavoro è completato quando viene identificata una causa riproducibile e viene documentata o convalidata una correzione per la chiusura intermittente del canale.